Merge pull request #1453 from xiaobo55x:cpuid

PiperOrigin-RevId: 294257911

7 files changed, 1656 insertions, 1092 deletions

diff --git a/pkg/cpuid/BUILD b/pkg/cpuid/BUILD
index 43a432190..d6cb1a549 100644
--- a/pkg/cpuid/BUILD
+++ b/pkg/cpuid/BUILD
@@ -7,6 +7,8 @@ go_library(
     srcs = [
         "cpu_amd64.s",
         "cpuid.go",
+        "cpuid_arm64.go",
+        "cpuid_x86.go",
     ],
     visibility = ["//:sandbox"],
     deps = ["//pkg/log"],
@@ -15,7 +17,10 @@ go_library(
 go_test(
     name = "cpuid_test",
     size = "small",
-    srcs = ["cpuid_test.go"],
+    srcs = [
+        "cpuid_arm64_test.go",
+        "cpuid_x86_test.go",
+    ],
     library = ":cpuid",
 )
 
@@ -23,7 +28,7 @@ go_test(
     name = "cpuid_parse_test",
     size = "small",
     srcs = [
-        "cpuid_parse_test.go",
+        "cpuid_parse_x86_test.go",
     ],
     library = ":cpuid",
     tags = ["manual"],
diff --git a/pkg/cpuid/cpuid.go b/pkg/cpuid/cpuid.go
index cf50ee53f..f7f9dbf86 100644
--- a/pkg/cpuid/cpuid.go
+++ b/pkg/cpuid/cpuid.go
@@ -1,4 +1,4 @@
-// Copyright 2018 The gVisor Authors.
+// Copyright 2019 The gVisor Authors.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -12,8 +12,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// +build i386 amd64
-
 // Package cpuid provides basic functionality for creating and adjusting CPU
 // feature sets.
 //
@@ -21,1100 +19,20 @@
 // known platform, or HostFeatureSet()) and then add, remove, and test for
 // features as desired.
 //
-// For example: Test for hardware extended state saving, and if we don't have
-// it, don't expose AVX, which cannot be saved with fxsave.
+// For example: on x86, test for hardware extended state saving, and if
+// we don't have it, don't expose AVX, which cannot be saved with fxsave.
 //
 //   if !HostFeatureSet().HasFeature(X86FeatureXSAVE) {
 //     exposedFeatures.Remove(X86FeatureAVX)
 //   }
 package cpuid
 
-import (
-	"bytes"
-	"fmt"
-	"io/ioutil"
-	"strconv"
-	"strings"
-
-	"gvisor.dev/gvisor/pkg/log"
-)
-
-// Common references for CPUID leaves and bits:
-//
-// Intel:
-//   * Intel SDM Volume 2, Chapter 3.2 "CPUID" (more up-to-date)
-//   * Intel Application Note 485 (more detailed)
-//
-// AMD:
-//   * AMD64 APM Volume 3, Appendix 3 "Obtaining Processor Information ..."
-
 // Feature is a unique identifier for a particular cpu feature. We just use an
-// int as a feature number on x86.
+// int as a feature number on x86 and arm64.
 //
-// Features are numbered according to "blocks". Each block is 32 bits, and
-// feature bits from the same source (cpuid leaf/level) are in the same block.
-type Feature int
-
-// block is a collection of 32 Feature bits.
-type block int
-
-const blockSize = 32
-
-// Feature bits are numbered according to "blocks". Each block is 32 bits, and
+// On x86, features are numbered according to "blocks". Each block is 32 bits, and
 // feature bits from the same source (cpuid leaf/level) are in the same block.
-func featureID(b block, bit int) Feature {
-	return Feature(32*int(b) + bit)
-}
-
-// Block 0 constants are all of the "basic" feature bits returned by a cpuid in
-// ecx with eax=1.
-const (
-	X86FeatureSSE3 Feature = iota
-	X86FeaturePCLMULDQ
-	X86FeatureDTES64
-	X86FeatureMONITOR
-	X86FeatureDSCPL
-	X86FeatureVMX
-	X86FeatureSMX
-	X86FeatureEST
-	X86FeatureTM2
-	X86FeatureSSSE3 // Not a typo, "supplemental" SSE3.
-	X86FeatureCNXTID
-	X86FeatureSDBG
-	X86FeatureFMA
-	X86FeatureCX16
-	X86FeatureXTPR
-	X86FeaturePDCM
-	_ // ecx bit 16 is reserved.
-	X86FeaturePCID
-	X86FeatureDCA
-	X86FeatureSSE4_1
-	X86FeatureSSE4_2
-	X86FeatureX2APIC
-	X86FeatureMOVBE
-	X86FeaturePOPCNT
-	X86FeatureTSCD
-	X86FeatureAES
-	X86FeatureXSAVE
-	X86FeatureOSXSAVE
-	X86FeatureAVX
-	X86FeatureF16C
-	X86FeatureRDRAND
-	_ // ecx bit 31 is reserved.
-)
-
-// Block 1 constants are all of the "basic" feature bits returned by a cpuid in
-// edx with eax=1.
-const (
-	X86FeatureFPU Feature = 32 + iota
-	X86FeatureVME
-	X86FeatureDE
-	X86FeaturePSE
-	X86FeatureTSC
-	X86FeatureMSR
-	X86FeaturePAE
-	X86FeatureMCE
-	X86FeatureCX8
-	X86FeatureAPIC
-	_ // edx bit 10 is reserved.
-	X86FeatureSEP
-	X86FeatureMTRR
-	X86FeaturePGE
-	X86FeatureMCA
-	X86FeatureCMOV
-	X86FeaturePAT
-	X86FeaturePSE36
-	X86FeaturePSN
-	X86FeatureCLFSH
-	_ // edx bit 20 is reserved.
-	X86FeatureDS
-	X86FeatureACPI
-	X86FeatureMMX
-	X86FeatureFXSR
-	X86FeatureSSE
-	X86FeatureSSE2
-	X86FeatureSS
-	X86FeatureHTT
-	X86FeatureTM
-	X86FeatureIA64
-	X86FeaturePBE
-)
-
-// Block 2 bits are the "structured extended" features returned in ebx for
-// eax=7, ecx=0.
-const (
-	X86FeatureFSGSBase Feature = 2*32 + iota
-	X86FeatureTSC_ADJUST
-	_ // ebx bit 2 is reserved.
-	X86FeatureBMI1
-	X86FeatureHLE
-	X86FeatureAVX2
-	X86FeatureFDP_EXCPTN_ONLY
-	X86FeatureSMEP
-	X86FeatureBMI2
-	X86FeatureERMS
-	X86FeatureINVPCID
-	X86FeatureRTM
-	X86FeatureCQM
-	X86FeatureFPCSDS
-	X86FeatureMPX
-	X86FeatureRDT
-	X86FeatureAVX512F
-	X86FeatureAVX512DQ
-	X86FeatureRDSEED
-	X86FeatureADX
-	X86FeatureSMAP
-	X86FeatureAVX512IFMA
-	X86FeaturePCOMMIT
-	X86FeatureCLFLUSHOPT
-	X86FeatureCLWB
-	X86FeatureIPT // Intel processor trace.
-	X86FeatureAVX512PF
-	X86FeatureAVX512ER
-	X86FeatureAVX512CD
-	X86FeatureSHA
-	X86FeatureAVX512BW
-	X86FeatureAVX512VL
-)
-
-// Block 3 bits are the "extended" features returned in ecx for eax=7, ecx=0.
-const (
-	X86FeaturePREFETCHWT1 Feature = 3*32 + iota
-	X86FeatureAVX512VBMI
-	X86FeatureUMIP
-	X86FeaturePKU
-	X86FeatureOSPKE
-	X86FeatureWAITPKG
-	X86FeatureAVX512_VBMI2
-	_ // ecx bit 7 is reserved
-	X86FeatureGFNI
-	X86FeatureVAES
-	X86FeatureVPCLMULQDQ
-	X86FeatureAVX512_VNNI
-	X86FeatureAVX512_BITALG
-	X86FeatureTME
-	X86FeatureAVX512_VPOPCNTDQ
-	_ // ecx bit 15 is reserved
-	X86FeatureLA57
-	// ecx bits 17-21 are reserved
-	_
-	_
-	_
-	_
-	_
-	X86FeatureRDPID
-	// ecx bits 23-24 are reserved
-	_
-	_
-	X86FeatureCLDEMOTE
-	_ // ecx bit 26 is reserved
-	X86FeatureMOVDIRI
-	X86FeatureMOVDIR64B
-)
-
-// Block 4 constants are for xsave capabilities in CPUID.(EAX=0DH,ECX=01H):EAX.
-// The CPUID leaf is available only if 'X86FeatureXSAVE' is present.
-const (
-	X86FeatureXSAVEOPT Feature = 4*32 + iota
-	X86FeatureXSAVEC
-	X86FeatureXGETBV1
-	X86FeatureXSAVES
-	// EAX[31:4] are reserved.
-)
-
-// Block 5 constants are the extended feature bits in
-// CPUID.(EAX=0x80000001):ECX.
-const (
-	X86FeatureLAHF64 Feature = 5*32 + iota
-	X86FeatureCMP_LEGACY
-	X86FeatureSVM
-	X86FeatureEXTAPIC
-	X86FeatureCR8_LEGACY
-	X86FeatureLZCNT
-	X86FeatureSSE4A
-	X86FeatureMISALIGNSSE
-	X86FeaturePREFETCHW
-	X86FeatureOSVW
-	X86FeatureIBS
-	X86FeatureXOP
-	X86FeatureSKINIT
-	X86FeatureWDT
-	_ // ecx bit 14 is reserved.
-	X86FeatureLWP
-	X86FeatureFMA4
-	X86FeatureTCE
-	_ // ecx bit 18 is reserved.
-	_ // ecx bit 19 is reserved.
-	_ // ecx bit 20 is reserved.
-	X86FeatureTBM
-	X86FeatureTOPOLOGY
-	X86FeaturePERFCTR_CORE
-	X86FeaturePERFCTR_NB
-	_ // ecx bit 25 is reserved.
-	X86FeatureBPEXT
-	X86FeaturePERFCTR_TSC
-	X86FeaturePERFCTR_LLC
-	X86FeatureMWAITX
-	// ECX[31:30] are reserved.
-)
-
-// Block 6 constants are the extended feature bits in
-// CPUID.(EAX=0x80000001):EDX.
 //
-// These are sparse, and so the bit positions are assigned manually.
-const (
-	// On AMD, EDX[24:23] | EDX[17:12] | EDX[9:0] are duplicate features
-	// also defined in block 1 (in identical bit positions). Those features
-	// are not listed here.
-	block6DuplicateMask = 0x183f3ff
-
-	X86FeatureSYSCALL  Feature = 6*32 + 11
-	X86FeatureNX       Feature = 6*32 + 20
-	X86FeatureMMXEXT   Feature = 6*32 + 22
-	X86FeatureFXSR_OPT Feature = 6*32 + 25
-	X86FeatureGBPAGES  Feature = 6*32 + 26
-	X86FeatureRDTSCP   Feature = 6*32 + 27
-	X86FeatureLM       Feature = 6*32 + 29
-	X86Feature3DNOWEXT Feature = 6*32 + 30
-	X86Feature3DNOW    Feature = 6*32 + 31
-)
-
-// linuxBlockOrder defines the order in which linux organizes the feature
-// blocks. Linux also tracks feature bits in 32-bit blocks, but in an order
-// which doesn't match well here, so for the /proc/cpuinfo generation we simply
-// re-map the blocks to Linux's ordering and then go through the bits in each
-// block.
-var linuxBlockOrder = []block{1, 6, 0, 5, 2, 4, 3}
-
-// To make emulation of /proc/cpuinfo easy, these names match the names of the
-// basic features in Linux defined in arch/x86/kernel/cpu/capflags.c.
-var x86FeatureStrings = map[Feature]string{
-	// Block 0.
-	X86FeatureSSE3:     "pni",
-	X86FeaturePCLMULDQ: "pclmulqdq",
-	X86FeatureDTES64:   "dtes64",
-	X86FeatureMONITOR:  "monitor",
-	X86FeatureDSCPL:    "ds_cpl",
-	X86FeatureVMX:      "vmx",
-	X86FeatureSMX:      "smx",
-	X86FeatureEST:      "est",
-	X86FeatureTM2:      "tm2",
-	X86FeatureSSSE3:    "ssse3",
-	X86FeatureCNXTID:   "cid",
-	X86FeatureSDBG:     "sdbg",
-	X86FeatureFMA:      "fma",
-	X86FeatureCX16:     "cx16",
-	X86FeatureXTPR:     "xtpr",
-	X86FeaturePDCM:     "pdcm",
-	X86FeaturePCID:     "pcid",
-	X86FeatureDCA:      "dca",
-	X86FeatureSSE4_1:   "sse4_1",
-	X86FeatureSSE4_2:   "sse4_2",
-	X86FeatureX2APIC:   "x2apic",
-	X86FeatureMOVBE:    "movbe",
-	X86FeaturePOPCNT:   "popcnt",
-	X86FeatureTSCD:     "tsc_deadline_timer",
-	X86FeatureAES:      "aes",
-	X86FeatureXSAVE:    "xsave",
-	X86FeatureAVX:      "avx",
-	X86FeatureF16C:     "f16c",
-	X86FeatureRDRAND:   "rdrand",
-
-	// Block 1.
-	X86FeatureFPU:   "fpu",
-	X86FeatureVME:   "vme",
-	X86FeatureDE:    "de",
-	X86FeaturePSE:   "pse",
-	X86FeatureTSC:   "tsc",
-	X86FeatureMSR:   "msr",
-	X86FeaturePAE:   "pae",
-	X86FeatureMCE:   "mce",
-	X86FeatureCX8:   "cx8",
-	X86FeatureAPIC:  "apic",
-	X86FeatureSEP:   "sep",
-	X86FeatureMTRR:  "mtrr",
-	X86FeaturePGE:   "pge",
-	X86FeatureMCA:   "mca",
-	X86FeatureCMOV:  "cmov",
-	X86FeaturePAT:   "pat",
-	X86FeaturePSE36: "pse36",
-	X86FeaturePSN:   "pn",
-	X86FeatureCLFSH: "clflush",
-	X86FeatureDS:    "dts",
-	X86FeatureACPI:  "acpi",
-	X86FeatureMMX:   "mmx",
-	X86FeatureFXSR:  "fxsr",
-	X86FeatureSSE:   "sse",
-	X86FeatureSSE2:  "sse2",
-	X86FeatureSS:    "ss",
-	X86FeatureHTT:   "ht",
-	X86FeatureTM:    "tm",
-	X86FeatureIA64:  "ia64",
-	X86FeaturePBE:   "pbe",
-
-	// Block 2.
-	X86FeatureFSGSBase:   "fsgsbase",
-	X86FeatureTSC_ADJUST: "tsc_adjust",
-	X86FeatureBMI1:       "bmi1",
-	X86FeatureHLE:        "hle",
-	X86FeatureAVX2:       "avx2",
-	X86FeatureSMEP:       "smep",
-	X86FeatureBMI2:       "bmi2",
-	X86FeatureERMS:       "erms",
-	X86FeatureINVPCID:    "invpcid",
-	X86FeatureRTM:        "rtm",
-	X86FeatureCQM:        "cqm",
-	X86FeatureMPX:        "mpx",
-	X86FeatureRDT:        "rdt_a",
-	X86FeatureAVX512F:    "avx512f",
-	X86FeatureAVX512DQ:   "avx512dq",
-	X86FeatureRDSEED:     "rdseed",
-	X86FeatureADX:        "adx",
-	X86FeatureSMAP:       "smap",
-	X86FeatureCLWB:       "clwb",
-	X86FeatureAVX512PF:   "avx512pf",
-	X86FeatureAVX512ER:   "avx512er",
-	X86FeatureAVX512CD:   "avx512cd",
-	X86FeatureSHA:        "sha_ni",
-	X86FeatureAVX512BW:   "avx512bw",
-	X86FeatureAVX512VL:   "avx512vl",
-
-	// Block 3.
-	X86FeatureAVX512VBMI:       "avx512vbmi",
-	X86FeatureUMIP:             "umip",
-	X86FeaturePKU:              "pku",
-	X86FeatureOSPKE:            "ospke",
-	X86FeatureWAITPKG:          "waitpkg",
-	X86FeatureAVX512_VBMI2:     "avx512_vbmi2",
-	X86FeatureGFNI:             "gfni",
-	X86FeatureVAES:             "vaes",
-	X86FeatureVPCLMULQDQ:       "vpclmulqdq",
-	X86FeatureAVX512_VNNI:      "avx512_vnni",
-	X86FeatureAVX512_BITALG:    "avx512_bitalg",
-	X86FeatureTME:              "tme",
-	X86FeatureAVX512_VPOPCNTDQ: "avx512_vpopcntdq",
-	X86FeatureLA57:             "la57",
-	X86FeatureRDPID:            "rdpid",
-	X86FeatureCLDEMOTE:         "cldemote",
-	X86FeatureMOVDIRI:          "movdiri",
-	X86FeatureMOVDIR64B:        "movdir64b",
-
-	// Block 4.
-	X86FeatureXSAVEOPT: "xsaveopt",
-	X86FeatureXSAVEC:   "xsavec",
-	X86FeatureXGETBV1:  "xgetbv1",
-	X86FeatureXSAVES:   "xsaves",
-
-	// Block 5.
-	X86FeatureLAHF64:       "lahf_lm", // LAHF/SAHF in long mode
-	X86FeatureCMP_LEGACY:   "cmp_legacy",
-	X86FeatureSVM:          "svm",
-	X86FeatureEXTAPIC:      "extapic",
-	X86FeatureCR8_LEGACY:   "cr8_legacy",
-	X86FeatureLZCNT:        "abm", // Advanced bit manipulation
-	X86FeatureSSE4A:        "sse4a",
-	X86FeatureMISALIGNSSE:  "misalignsse",
-	X86FeaturePREFETCHW:    "3dnowprefetch",
-	X86FeatureOSVW:         "osvw",
-	X86FeatureIBS:          "ibs",
-	X86FeatureXOP:          "xop",
-	X86FeatureSKINIT:       "skinit",
-	X86FeatureWDT:          "wdt",
-	X86FeatureLWP:          "lwp",
-	X86FeatureFMA4:         "fma4",
-	X86FeatureTCE:          "tce",
-	X86FeatureTBM:          "tbm",
-	X86FeatureTOPOLOGY:     "topoext",
-	X86FeaturePERFCTR_CORE: "perfctr_core",
-	X86FeaturePERFCTR_NB:   "perfctr_nb",
-	X86FeatureBPEXT:        "bpext",
-	X86FeaturePERFCTR_TSC:  "ptsc",
-	X86FeaturePERFCTR_LLC:  "perfctr_llc",
-	X86FeatureMWAITX:       "mwaitx",
-
-	// Block 6.
-	X86FeatureSYSCALL:  "syscall",
-	X86FeatureNX:       "nx",
-	X86FeatureMMXEXT:   "mmxext",
-	X86FeatureFXSR_OPT: "fxsr_opt",
-	X86FeatureGBPAGES:  "pdpe1gb",
-	X86FeatureRDTSCP:   "rdtscp",
-	X86FeatureLM:       "lm",
-	X86Feature3DNOWEXT: "3dnowext",
-	X86Feature3DNOW:    "3dnow",
-}
-
-// These flags are parse only---they can be used for setting / unsetting the
-// flags, but will not get printed out in /proc/cpuinfo.
-var x86FeatureParseOnlyStrings = map[Feature]string{
-	// Block 0.
-	X86FeatureOSXSAVE: "osxsave",
-
-	// Block 2.
-	X86FeatureFDP_EXCPTN_ONLY: "fdp_excptn_only",
-	X86FeatureFPCSDS:          "fpcsds",
-	X86FeatureIPT:             "pt",
-	X86FeatureCLFLUSHOPT:      "clfushopt",
-
-	// Block 3.
-	X86FeaturePREFETCHWT1: "prefetchwt1",
-}
-
-// intelCacheDescriptors describe the caches and TLBs on the system. They are
-// returned in the registers for eax=2. Intel only.
-type intelCacheDescriptor uint8
-
-// Valid cache/TLB descriptors. All descriptors can be found in Intel SDM Vol.
-// 2, Ch. 3.2, "CPUID", Table 3-12 "Encoding of CPUID Leaf 2 Descriptors".
-const (
-	intelNullDescriptor    intelCacheDescriptor = 0
-	intelNoTLBDescriptor   intelCacheDescriptor = 0xfe
-	intelNoCacheDescriptor intelCacheDescriptor = 0xff
-
-	// Most descriptors omitted for brevity as they are currently unused.
-)
-
-// CacheType describes the type of a cache, as returned in eax[4:0] for eax=4.
-type CacheType uint8
-
-const (
-	// cacheNull indicates that there are no more entries.
-	cacheNull CacheType = iota
-
-	// CacheData is a data cache.
-	CacheData
-
-	// CacheInstruction is an instruction cache.
-	CacheInstruction
-
-	// CacheUnified is a unified instruction and data cache.
-	CacheUnified
-)
-
-// Cache describes the parameters of a single cache on the system.
-//
-// +stateify savable
-type Cache struct {
-	// Level is the hierarchical level of this cache (L1, L2, etc).
-	Level uint32
-
-	// Type is the type of cache.
-	Type CacheType
-
-	// FullyAssociative indicates that entries may be placed in any block.
-	FullyAssociative bool
-
-	// Partitions is the number of physical partitions in the cache.
-	Partitions uint32
-
-	// Ways is the number of ways of associativity in the cache.
-	Ways uint32
-
-	// Sets is the number of sets in the cache.
-	Sets uint32
-
-	// InvalidateHierarchical indicates that WBINVD/INVD from threads
-	// sharing this cache acts upon lower level caches for threads sharing
-	// this cache.
-	InvalidateHierarchical bool
-
-	// Inclusive indicates that this cache is inclusive of lower cache
-	// levels.
-	Inclusive bool
-
-	// DirectMapped indicates that this cache is directly mapped from
-	// address, rather than using a hash function.
-	DirectMapped bool
-}
-
-// Just a way to wrap cpuid function numbers.
-type cpuidFunction uint32
-
-// The constants below are the lower or "standard" cpuid functions, ordered as
-// defined by the hardware.
-const (
-	vendorID                      cpuidFunction = iota // Returns vendor ID and largest standard function.
-	featureInfo                                        // Returns basic feature bits and processor signature.
-	intelCacheDescriptors                              // Returns list of cache descriptors. Intel only.
-	intelSerialNumber                                  // Returns processor serial number (obsolete on new hardware). Intel only.
-	intelDeterministicCacheParams                      // Returns deterministic cache information. Intel only.
-	monitorMwaitParams                                 // Returns information about monitor/mwait instructions.
-	powerParams                                        // Returns information about power management and thermal sensors.
-	extendedFeatureInfo                                // Returns extended feature bits.
-	_                                                  // Function 0x8 is reserved.
-	intelDCAParams                                     // Returns direct cache access information. Intel only.
-	intelPMCInfo                                       // Returns information about performance monitoring features. Intel only.
-	intelX2APICInfo                                    // Returns core/logical processor topology. Intel only.
-	_                                                  // Function 0xc is reserved.
-	xSaveInfo                                          // Returns information about extended state management.
-)
-
-// The "extended" functions start at 0x80000000.
-const (
-	extendedFunctionInfo cpuidFunction = 0x80000000 + iota // Returns highest available extended function in eax.
-	extendedFeatures                                       // Returns some extended feature bits in edx and ecx.
-)
-
-// These are the extended floating point state features. They are used to
-// enumerate floating point features in XCR0, XSTATE_BV, etc.
-const (
-	XSAVEFeatureX87         = 1 << 0
-	XSAVEFeatureSSE         = 1 << 1
-	XSAVEFeatureAVX         = 1 << 2
-	XSAVEFeatureBNDREGS     = 1 << 3
-	XSAVEFeatureBNDCSR      = 1 << 4
-	XSAVEFeatureAVX512op    = 1 << 5
-	XSAVEFeatureAVX512zmm0  = 1 << 6
-	XSAVEFeatureAVX512zmm16 = 1 << 7
-	XSAVEFeaturePKRU        = 1 << 9
-)
-
-var cpuFreqMHz float64
-
-// x86FeaturesFromString includes features from x86FeatureStrings and
-// x86FeatureParseOnlyStrings.
-var x86FeaturesFromString = make(map[string]Feature)
-
-// FeatureFromString returns the Feature associated with the given feature
-// string plus a bool to indicate if it could find the feature.
-func FeatureFromString(s string) (Feature, bool) {
-	f, b := x86FeaturesFromString[s]
-	return f, b
-}
-
-// String implements fmt.Stringer.
-func (f Feature) String() string {
-	if s := f.flagString(false); s != "" {
-		return s
-	}
-
-	block := int(f) / 32
-	bit := int(f) % 32
-	return fmt.Sprintf("<cpuflag %d; block %d bit %d>", f, block, bit)
-}
-
-func (f Feature) flagString(cpuinfoOnly bool) string {
-	if s, ok := x86FeatureStrings[f]; ok {
-		return s
-	}
-	if !cpuinfoOnly {
-		return x86FeatureParseOnlyStrings[f]
-	}
-	return ""
-}
-
-// FeatureSet is a set of Features for a CPU.
-//
-// +stateify savable
-type FeatureSet struct {
-	// Set is the set of features that are enabled in this FeatureSet.
-	Set map[Feature]bool
-
-	// VendorID is the 12-char string returned in ebx:edx:ecx for eax=0.
-	VendorID string
-
-	// ExtendedFamily is part of the processor signature.
-	ExtendedFamily uint8
-
-	// ExtendedModel is part of the processor signature.
-	ExtendedModel uint8
-
-	// ProcessorType is part of the processor signature.
-	ProcessorType uint8
-
-	// Family is part of the processor signature.
-	Family uint8
-
-	// Model is part of the processor signature.
-	Model uint8
-
-	// SteppingID is part of the processor signature.
-	SteppingID uint8
-
-	// Caches describes the caches on the CPU.
-	Caches []Cache
-
-	// CacheLine is the size of a cache line in bytes.
-	//
-	// All caches use the same line size. This is not enforced in the CPUID
-	// encoding, but is true on all known x86 processors.
-	CacheLine uint32
-}
-
-// FlagsString prints out supported CPU flags. If cpuinfoOnly is true, it is
-// equivalent to the "flags" field in /proc/cpuinfo.
-func (fs *FeatureSet) FlagsString(cpuinfoOnly bool) string {
-	var s []string
-	for _, b := range linuxBlockOrder {
-		for i := 0; i < blockSize; i++ {
-			if f := featureID(b, i); fs.Set[f] {
-				if fstr := f.flagString(cpuinfoOnly); fstr != "" {
-					s = append(s, fstr)
-				}
-			}
-		}
-	}
-	return strings.Join(s, " ")
-}
-
-// WriteCPUInfoTo is to generate a section of one cpu in /proc/cpuinfo. This is
-// a minimal /proc/cpuinfo, it is missing some fields like "microcode" that are
-// not always printed in Linux. The bogomips field is simply made up.
-func (fs FeatureSet) WriteCPUInfoTo(cpu uint, b *bytes.Buffer) {
-	fmt.Fprintf(b, "processor\t: %d\n", cpu)
-	fmt.Fprintf(b, "vendor_id\t: %s\n", fs.VendorID)
-	fmt.Fprintf(b, "cpu family\t: %d\n", ((fs.ExtendedFamily<<4)&0xff)|fs.Family)
-	fmt.Fprintf(b, "model\t\t: %d\n", ((fs.ExtendedModel<<4)&0xff)|fs.Model)
-	fmt.Fprintf(b, "model name\t: %s\n", "unknown") // Unknown for now.
-	fmt.Fprintf(b, "stepping\t: %s\n", "unknown")   // Unknown for now.
-	fmt.Fprintf(b, "cpu MHz\t\t: %.3f\n", cpuFreqMHz)
-	fmt.Fprintln(b, "fpu\t\t: yes")
-	fmt.Fprintln(b, "fpu_exception\t: yes")
-	fmt.Fprintf(b, "cpuid level\t: %d\n", uint32(xSaveInfo)) // Same as ax in vendorID.
-	fmt.Fprintln(b, "wp\t\t: yes")
-	fmt.Fprintf(b, "flags\t\t: %s\n", fs.FlagsString(true))
-	fmt.Fprintf(b, "bogomips\t: %.02f\n", cpuFreqMHz) // It's bogus anyway.
-	fmt.Fprintf(b, "clflush size\t: %d\n", fs.CacheLine)
-	fmt.Fprintf(b, "cache_alignment\t: %d\n", fs.CacheLine)
-	fmt.Fprintf(b, "address sizes\t: %d bits physical, %d bits virtual\n", 46, 48)
-	fmt.Fprintln(b, "power management:") // This is always here, but can be blank.
-	fmt.Fprintln(b, "")                  // The /proc/cpuinfo file ends with an extra newline.
-}
-
-const (
-	amdVendorID   = "AuthenticAMD"
-	intelVendorID = "GenuineIntel"
-)
-
-// AMD returns true if fs describes an AMD CPU.
-func (fs *FeatureSet) AMD() bool {
-	return fs.VendorID == amdVendorID
-}
-
-// Intel returns true if fs describes an Intel CPU.
-func (fs *FeatureSet) Intel() bool {
-	return fs.VendorID == intelVendorID
-}
-
-// ErrIncompatible is returned by FeatureSet.HostCompatible if fs is not a
-// subset of the host feature set.
-type ErrIncompatible struct {
-	message string
-}
-
-// Error implements error.
-func (e ErrIncompatible) Error() string {
-	return e.message
-}
-
-// CheckHostCompatible returns nil if fs is a subset of the host feature set.
-func (fs *FeatureSet) CheckHostCompatible() error {
-	hfs := HostFeatureSet()
-
-	if diff := fs.Subtract(hfs); diff != nil {
-		return ErrIncompatible{fmt.Sprintf("CPU feature set %v incompatible with host feature set %v (missing: %v)", fs.FlagsString(false), hfs.FlagsString(false), diff)}
-	}
-
-	// The size of a cache line must match, as it is critical to correctly
-	// utilizing CLFLUSH. Other cache properties are allowed to change, as
-	// they are not important to correctness.
-	if fs.CacheLine != hfs.CacheLine {
-		return ErrIncompatible{fmt.Sprintf("CPU cache line size %d incompatible with host cache line size %d", fs.CacheLine, hfs.CacheLine)}
-	}
-
-	return nil
-}
-
-// Helper to convert 3 regs into 12-byte vendor ID.
-func vendorIDFromRegs(bx, cx, dx uint32) string {
-	bytes := make([]byte, 0, 12)
-	for i := uint(0); i < 4; i++ {
-		b := byte(bx >> (i * 8))
-		bytes = append(bytes, b)
-	}
-
-	for i := uint(0); i < 4; i++ {
-		b := byte(dx >> (i * 8))
-		bytes = append(bytes, b)
-	}
-
-	for i := uint(0); i < 4; i++ {
-		b := byte(cx >> (i * 8))
-		bytes = append(bytes, b)
-	}
-	return string(bytes)
-}
-
-// ExtendedStateSize returns the number of bytes needed to save the "extended
-// state" for this processor and the boundary it must be aligned to. Extended
-// state includes floating point registers, and other cpu state that's not
-// associated with the normal task context.
-//
-// Note: We can save some space here with an optimization where we use a
-// smaller chunk of memory depending on features that are actually enabled.
-// Currently we just use the largest possible size for simplicity (which is
-// about 2.5K worst case, with avx512).
-func (fs *FeatureSet) ExtendedStateSize() (size, align uint) {
-	if fs.UseXsave() {
-		// Leaf 0 of xsaveinfo function returns the size for currently
-		// enabled xsave features in ebx, the maximum size if all valid
-		// features are saved with xsave in ecx, and valid XCR0 bits in
-		// edx:eax.
-		_, _, maxSize, _ := HostID(uint32(xSaveInfo), 0)
-		return uint(maxSize), 64
-	}
-
-	// If we don't support xsave, we fall back to fxsave, which requires
-	// 512 bytes aligned to 16 bytes.
-	return 512, 16
-}
-
-// ValidXCR0Mask returns the bits that may be set to 1 in control register
-// XCR0.
-func (fs *FeatureSet) ValidXCR0Mask() uint64 {
-	if !fs.UseXsave() {
-		return 0
-	}
-	eax, _, _, edx := HostID(uint32(xSaveInfo), 0)
-	return uint64(edx)<<32 | uint64(eax)
-}
-
-// vendorIDRegs returns the 3 register values used to construct the 12-byte
-// vendor ID string for eax=0.
-func (fs *FeatureSet) vendorIDRegs() (bx, dx, cx uint32) {
-	for i := uint(0); i < 4; i++ {
-		bx |= uint32(fs.VendorID[i]) << (i * 8)
-	}
-
-	for i := uint(0); i < 4; i++ {
-		dx |= uint32(fs.VendorID[i+4]) << (i * 8)
-	}
-
-	for i := uint(0); i < 4; i++ {
-		cx |= uint32(fs.VendorID[i+8]) << (i * 8)
-	}
-	return
-}
-
-// signature returns the signature dword that's returned in eax when eax=1.
-func (fs *FeatureSet) signature() uint32 {
-	var s uint32
-	s |= uint32(fs.SteppingID & 0xf)
-	s |= uint32(fs.Model&0xf) << 4
-	s |= uint32(fs.Family&0xf) << 8
-	s |= uint32(fs.ProcessorType&0x3) << 12
-	s |= uint32(fs.ExtendedModel&0xf) << 16
-	s |= uint32(fs.ExtendedFamily&0xff) << 20
-	return s
-}
-
-// Helper to deconstruct signature dword.
-func signatureSplit(v uint32) (ef, em, pt, f, m, sid uint8) {
-	sid = uint8(v & 0xf)
-	m = uint8(v>>4) & 0xf
-	f = uint8(v>>8) & 0xf
-	pt = uint8(v>>12) & 0x3
-	em = uint8(v>>16) & 0xf
-	ef = uint8(v >> 20)
-	return
-}
-
-// Helper to convert blockwise feature bit masks into a set of features. Masks
-// must be provided in order for each block, without skipping them. If a block
-// does not matter for this feature set, 0 is specified.
-func setFromBlockMasks(blocks ...uint32) map[Feature]bool {
-	s := make(map[Feature]bool)
-	for b, blockMask := range blocks {
-		for i := 0; i < blockSize; i++ {
-			if blockMask&1 != 0 {
-				s[featureID(block(b), i)] = true
-			}
-			blockMask >>= 1
-		}
-	}
-	return s
-}
-
-// blockMask returns the 32-bit mask associated with a block of features.
-func (fs *FeatureSet) blockMask(b block) uint32 {
-	var mask uint32
-	for i := 0; i < blockSize; i++ {
-		if fs.Set[featureID(b, i)] {
-			mask |= 1 << uint(i)
-		}
-	}
-	return mask
-}
-
-// Remove removes a Feature from a FeatureSet. It ignores features
-// that are not in the FeatureSet.
-func (fs *FeatureSet) Remove(feature Feature) {
-	delete(fs.Set, feature)
-}
-
-// Add adds a Feature to a FeatureSet. It ignores duplicate features.
-func (fs *FeatureSet) Add(feature Feature) {
-	fs.Set[feature] = true
-}
-
-// HasFeature tests whether or not a feature is in the given feature set.
-func (fs *FeatureSet) HasFeature(feature Feature) bool {
-	return fs.Set[feature]
-}
-
-// Subtract returns the features present in fs that are not present in other.
-// If all features in fs are present in other, Subtract returns nil.
-func (fs *FeatureSet) Subtract(other *FeatureSet) (diff map[Feature]bool) {
-	for f := range fs.Set {
-		if !other.Set[f] {
-			if diff == nil {
-				diff = make(map[Feature]bool)
-			}
-			diff[f] = true
-		}
-	}
-
-	return
-}
-
-// EmulateID emulates a cpuid instruction based on the feature set.
-func (fs *FeatureSet) EmulateID(origAx, origCx uint32) (ax, bx, cx, dx uint32) {
-	switch cpuidFunction(origAx) {
-	case vendorID:
-		ax = uint32(xSaveInfo) // 0xd (xSaveInfo) is the highest function we support.
-		bx, dx, cx = fs.vendorIDRegs()
-	case featureInfo:
-		// CLFLUSH line size is encoded in quadwords. Other fields in bx unsupported.
-		bx = (fs.CacheLine / 8) << 8
-		cx = fs.blockMask(block(0))
-		dx = fs.blockMask(block(1))
-		ax = fs.signature()
-	case intelCacheDescriptors:
-		if !fs.Intel() {
-			// Reserved on non-Intel.
-			return 0, 0, 0, 0
-		}
-
-		// "The least-significant byte in register EAX (register AL)
-		// will always return 01H. Software should ignore this value
-		// and not interpret it as an informational descriptor." - SDM
-		//
-		// We only support reporting cache parameters via
-		// intelDeterministicCacheParams; report as much here.
-		//
-		// We do not support exposing TLB information at all.
-		ax = 1 | (uint32(intelNoCacheDescriptor) << 8)
-	case intelDeterministicCacheParams:
-		if !fs.Intel() {
-			// Reserved on non-Intel.
-			return 0, 0, 0, 0
-		}
-
-		// cx is the index of the cache to describe.
-		if int(origCx) >= len(fs.Caches) {
-			return uint32(cacheNull), 0, 0, 0
-		}
-		c := fs.Caches[origCx]
-
-		ax = uint32(c.Type)
-		ax |= c.Level << 5
-		ax |= 1 << 8 // Always claim the cache is "self-initializing".
-		if c.FullyAssociative {
-			ax |= 1 << 9
-		}
-		// Processor topology not supported.
-
-		bx = fs.CacheLine - 1
-		bx |= (c.Partitions - 1) << 12
-		bx |= (c.Ways - 1) << 22
-
-		cx = c.Sets - 1
-
-		if !c.InvalidateHierarchical {
-			dx |= 1
-		}
-		if c.Inclusive {
-			dx |= 1 << 1
-		}
-		if !c.DirectMapped {
-			dx |= 1 << 2
-		}
-	case xSaveInfo:
-		if !fs.UseXsave() {
-			return 0, 0, 0, 0
-		}
-		return HostID(uint32(xSaveInfo), origCx)
-	case extendedFeatureInfo:
-		if origCx != 0 {
-			break // Only leaf 0 is supported.
-		}
-		bx = fs.blockMask(block(2))
-		cx = fs.blockMask(block(3))
-	case extendedFunctionInfo:
-		// We only support showing the extended features.
-		ax = uint32(extendedFeatures)
-		cx = 0
-	case extendedFeatures:
-		cx = fs.blockMask(block(5))
-		dx = fs.blockMask(block(6))
-		if fs.AMD() {
-			// AMD duplicates some block 1 features in block 6.
-			dx |= fs.blockMask(block(1)) & block6DuplicateMask
-		}
-	}
-
-	return
-}
-
-// UseXsave returns the choice of fp state saving instruction.
-func (fs *FeatureSet) UseXsave() bool {
-	return fs.HasFeature(X86FeatureXSAVE) && fs.HasFeature(X86FeatureOSXSAVE)
-}
-
-// UseXsaveopt returns true if 'fs' supports the "xsaveopt" instruction.
-func (fs *FeatureSet) UseXsaveopt() bool {
-	return fs.UseXsave() && fs.HasFeature(X86FeatureXSAVEOPT)
-}
-
-// HostID executes a native CPUID instruction.
-func HostID(axArg, cxArg uint32) (ax, bx, cx, dx uint32)
-
-// HostFeatureSet uses cpuid to get host values and construct a feature set
-// that matches that of the host machine. Note that there are several places
-// where there appear to be some unnecessary assignments between register names
-// (ax, bx, cx, or dx) and featureBlockN variables. This is to explicitly show
-// where the different feature blocks come from, to make the code easier to
-// inspect and read.
-func HostFeatureSet() *FeatureSet {
-	// eax=0 gets max supported feature and vendor ID.
-	_, bx, cx, dx := HostID(0, 0)
-	vendorID := vendorIDFromRegs(bx, cx, dx)
-
-	// eax=1 gets basic features in ecx:edx.
-	ax, bx, cx, dx := HostID(1, 0)
-	featureBlock0 := cx
-	featureBlock1 := dx
-	ef, em, pt, f, m, sid := signatureSplit(ax)
-	cacheLine := 8 * (bx >> 8) & 0xff
-
-	// eax=4, ecx=i gets details about cache index i. Only supported on Intel.
-	var caches []Cache
-	if vendorID == intelVendorID {
-		// ecx selects the cache index until a null type is returned.
-		for i := uint32(0); ; i++ {
-			ax, bx, cx, dx := HostID(4, i)
-			t := CacheType(ax & 0xf)
-			if t == cacheNull {
-				break
-			}
-
-			lineSize := (bx & 0xfff) + 1
-			if lineSize != cacheLine {
-				panic(fmt.Sprintf("Mismatched cache line size: %d vs %d", lineSize, cacheLine))
-			}
-
-			caches = append(caches, Cache{
-				Type:                   t,
-				Level:                  (ax >> 5) & 0x7,
-				FullyAssociative:       ((ax >> 9) & 1) == 1,
-				Partitions:             ((bx >> 12) & 0x3ff) + 1,
-				Ways:                   ((bx >> 22) & 0x3ff) + 1,
-				Sets:                   cx + 1,
-				InvalidateHierarchical: (dx & 1) == 0,
-				Inclusive:              ((dx >> 1) & 1) == 1,
-				DirectMapped:           ((dx >> 2) & 1) == 0,
-			})
-		}
-	}
-
-	// eax=7, ecx=0 gets extended features in ecx:ebx.
-	_, bx, cx, _ = HostID(7, 0)
-	featureBlock2 := bx
-	featureBlock3 := cx
-
-	// Leaf 0xd is supported only if CPUID.1:ECX.XSAVE[bit 26] is set.
-	var featureBlock4 uint32
-	if (featureBlock0 & (1 << 26)) != 0 {
-		featureBlock4, _, _, _ = HostID(uint32(xSaveInfo), 1)
-	}
-
-	// eax=0x80000000 gets supported extended levels. We use this to
-	// determine if there are any non-zero block 4 or block 6 bits to find.
-	var featureBlock5, featureBlock6 uint32
-	if ax, _, _, _ := HostID(uint32(extendedFunctionInfo), 0); ax >= uint32(extendedFeatures) {
-		// eax=0x80000001 gets AMD added feature bits.
-		_, _, cx, dx = HostID(uint32(extendedFeatures), 0)
-		featureBlock5 = cx
-		// Ignore features duplicated from block 1 on AMD. These bits
-		// are reserved on Intel.
-		featureBlock6 = dx &^ block6DuplicateMask
-	}
-
-	set := setFromBlockMasks(featureBlock0, featureBlock1, featureBlock2, featureBlock3, featureBlock4, featureBlock5, featureBlock6)
-	return &FeatureSet{
-		Set:            set,
-		VendorID:       vendorID,
-		ExtendedFamily: ef,
-		ExtendedModel:  em,
-		ProcessorType:  pt,
-		Family:         f,
-		Model:          m,
-		SteppingID:     sid,
-		CacheLine:      cacheLine,
-		Caches:         caches,
-	}
-}
-
-// Reads max cpu frequency from host /proc/cpuinfo. Must run before
-// whitelisting. This value is used to create the fake /proc/cpuinfo from a
-// FeatureSet.
-func initCPUFreq() {
-	cpuinfob, err := ioutil.ReadFile("/proc/cpuinfo")
-	if err != nil {
-		// Leave it as 0... The standalone VDSO bails out in the same
-		// way.
-		log.Warningf("Could not read /proc/cpuinfo: %v", err)
-		return
-	}
-	cpuinfo := string(cpuinfob)
-
-	// We get the value straight from host /proc/cpuinfo. On machines with
-	// frequency scaling enabled, this will only get the current value
-	// which will likely be inaccurate. This is fine on machines with
-	// frequency scaling disabled.
-	for _, line := range strings.Split(cpuinfo, "\n") {
-		if strings.Contains(line, "cpu MHz") {
-			splitMHz := strings.Split(line, ":")
-			if len(splitMHz) < 2 {
-				log.Warningf("Could not read /proc/cpuinfo: malformed cpu MHz line")
-				return
-			}
-
-			// If there was a problem, leave cpuFreqMHz as 0.
-			var err error
-			cpuFreqMHz, err = strconv.ParseFloat(strings.TrimSpace(splitMHz[1]), 64)
-			if err != nil {
-				log.Warningf("Could not parse cpu MHz value %v: %v", splitMHz[1], err)
-				cpuFreqMHz = 0
-				return
-			}
-			return
-		}
-	}
-	log.Warningf("Could not parse /proc/cpuinfo, it is empty or does not contain cpu MHz")
-}
-
-func initFeaturesFromString() {
-	for f, s := range x86FeatureStrings {
-		x86FeaturesFromString[s] = f
-	}
-	for f, s := range x86FeatureParseOnlyStrings {
-		x86FeaturesFromString[s] = f
-	}
-}
-
-func init() {
-	// initCpuFreq must be run before whitelists are enabled.
-	initCPUFreq()
-	initFeaturesFromString()
-}
+// On arm64, features are numbered according to the ELF HWCAP definition.
+// arch/arm64/include/uapi/asm/hwcap.h
+type Feature int
diff --git a/pkg/cpuid/cpuid_arm64.go b/pkg/cpuid/cpuid_arm64.go
new file mode 100644
index 000000000..08381c1c0
--- /dev/null
+++ b/pkg/cpuid/cpuid_arm64.go
@@ -0,0 +1,482 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build arm64
+
+package cpuid
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"io/ioutil"
+	"strconv"
+	"strings"
+
+	"gvisor.dev/gvisor/pkg/log"
+)
+
+// ARM64 doesn't have a 'cpuid' equivalent, which means it have no architected
+// discovery mechanism for hardware features available to userspace code at EL0.
+// The kernel exposes the presence of these features to userspace through a set
+// of flags(HWCAP/HWCAP2) bits, exposed in the auxilliary vector.
+// Ref Documentation/arm64/elf_hwcaps.rst for more info.
+//
+// Currently, only the HWCAP bits are supported.
+
+const (
+	// ARM64FeatureFP indicates support for single and double precision
+	// float point types.
+	ARM64FeatureFP Feature = iota
+
+	// ARM64FeatureASIMD indicates support for Advanced SIMD with single
+	// and double precision float point arithmetic.
+	ARM64FeatureASIMD
+
+	// ARM64FeatureEVTSTRM indicates support for the generic timer
+	// configured to generate events at a frequency of approximately
+	// 100KHz.
+	ARM64FeatureEVTSTRM
+
+	// ARM64FeatureAES indicates support for AES instructions
+	// (AESE/AESD/AESMC/AESIMC).
+	ARM64FeatureAES
+
+	// ARM64FeaturePMULL indicates support for AES instructions
+	// (PMULL/PMULL2).
+	ARM64FeaturePMULL
+
+	// ARM64FeatureSHA1 indicates support for SHA1 instructions
+	// (SHA1C/SHA1P/SHA1M etc).
+	ARM64FeatureSHA1
+
+	// ARM64FeatureSHA2 indicates support for SHA2 instructions
+	// (SHA256H/SHA256H2/SHA256SU0 etc).
+	ARM64FeatureSHA2
+
+	// ARM64FeatureCRC32 indicates support for CRC32 instructions
+	// (CRC32B/CRC32H/CRC32W etc).
+	ARM64FeatureCRC32
+
+	// ARM64FeatureATOMICS indicates support for atomic instructions
+	// (LDADD/LDCLR/LDEOR/LDSET etc).
+	ARM64FeatureATOMICS
+
+	// ARM64FeatureFPHP indicates support for half precision float point
+	// arithmetic.
+	ARM64FeatureFPHP
+
+	// ARM64FeatureASIMDHP indicates support for ASIMD with half precision
+	// float point arithmetic.
+	ARM64FeatureASIMDHP
+
+	// ARM64FeatureCPUID indicates support for EL0 access to certain ID
+	// registers is available.
+	ARM64FeatureCPUID
+
+	// ARM64FeatureASIMDRDM indicates support for SQRDMLAH and SQRDMLSH
+	// instructions.
+	ARM64FeatureASIMDRDM
+
+	// ARM64FeatureJSCVT indicates support for the FJCVTZS instruction.
+	ARM64FeatureJSCVT
+
+	// ARM64FeatureFCMA indicates support for the FCMLA and FCADD
+	// instructions.
+	ARM64FeatureFCMA
+
+	// ARM64FeatureLRCPC indicates support for the LDAPRB/LDAPRH/LDAPR
+	// instructions.
+	ARM64FeatureLRCPC
+
+	// ARM64FeatureDCPOP indicates support for DC instruction (DC CVAP).
+	ARM64FeatureDCPOP
+
+	// ARM64FeatureSHA3 indicates support for SHA3 instructions
+	// (EOR3/RAX1/XAR/BCAX).
+	ARM64FeatureSHA3
+
+	// ARM64FeatureSM3 indicates support for SM3 instructions
+	// (SM3SS1/SM3TT1A/SM3TT1B).
+	ARM64FeatureSM3
+
+	// ARM64FeatureSM4 indicates support for SM4 instructions
+	// (SM4E/SM4EKEY).
+	ARM64FeatureSM4
+
+	// ARM64FeatureASIMDDP indicates support for dot product instructions
+	// (UDOT/SDOT).
+	ARM64FeatureASIMDDP
+
+	// ARM64FeatureSHA512 indicates support for SHA2 instructions
+	// (SHA512H/SHA512H2/SHA512SU0).
+	ARM64FeatureSHA512
+
+	// ARM64FeatureSVE indicates support for Scalable Vector Extension.
+	ARM64FeatureSVE
+
+	// ARM64FeatureASIMDFHM indicates support for FMLAL and FMLSL
+	// instructions.
+	ARM64FeatureASIMDFHM
+)
+
+// ELF auxiliary vector tags
+const (
+	_AT_NULL   = 0  // End of vector
+	_AT_HWCAP  = 16 // hardware capability bit vector
+	_AT_HWCAP2 = 26 // hardware capability bit vector 2
+)
+
+// These should not be changed after they are initialized.
+var hwCap uint
+
+// To make emulation of /proc/cpuinfo easy, these names match the names of the
+// basic features in Linux defined in arch/arm64/kernel/cpuinfo.c.
+var arm64FeatureStrings = map[Feature]string{
+	ARM64FeatureFP:       "fp",
+	ARM64FeatureASIMD:    "asimd",
+	ARM64FeatureEVTSTRM:  "evtstrm",
+	ARM64FeatureAES:      "aes",
+	ARM64FeaturePMULL:    "pmull",
+	ARM64FeatureSHA1:     "sha1",
+	ARM64FeatureSHA2:     "sha2",
+	ARM64FeatureCRC32:    "crc32",
+	ARM64FeatureATOMICS:  "atomics",
+	ARM64FeatureFPHP:     "fphp",
+	ARM64FeatureASIMDHP:  "asimdhp",
+	ARM64FeatureCPUID:    "cpuid",
+	ARM64FeatureASIMDRDM: "asimdrdm",
+	ARM64FeatureJSCVT:    "jscvt",
+	ARM64FeatureFCMA:     "fcma",
+	ARM64FeatureLRCPC:    "lrcpc",
+	ARM64FeatureDCPOP:    "dcpop",
+	ARM64FeatureSHA3:     "sha3",
+	ARM64FeatureSM3:      "sm3",
+	ARM64FeatureSM4:      "sm4",
+	ARM64FeatureASIMDDP:  "asimddp",
+	ARM64FeatureSHA512:   "sha512",
+	ARM64FeatureSVE:      "sve",
+	ARM64FeatureASIMDFHM: "asimdfhm",
+}
+
+var (
+	cpuFreqMHz float64
+	cpuImplHex uint64
+	cpuArchDec uint64
+	cpuVarHex  uint64
+	cpuPartHex uint64
+	cpuRevDec  uint64
+)
+
+// arm64FeaturesFromString includes features from arm64FeatureStrings.
+var arm64FeaturesFromString = make(map[string]Feature)
+
+// FeatureFromString returns the Feature associated with the given feature
+// string plus a bool to indicate if it could find the feature.
+func FeatureFromString(s string) (Feature, bool) {
+	f, b := arm64FeaturesFromString[s]
+	return f, b
+}
+
+// String implements fmt.Stringer.
+func (f Feature) String() string {
+	if s := f.flagString(); s != "" {
+		return s
+	}
+
+	return fmt.Sprintf("<cpuflag %d>", f)
+}
+
+func (f Feature) flagString() string {
+	if s, ok := arm64FeatureStrings[f]; ok {
+		return s
+	}
+
+	return ""
+}
+
+// FeatureSet is a set of Features for a CPU.
+//
+// +stateify savable
+type FeatureSet struct {
+	// Set is the set of features that are enabled in this FeatureSet.
+	Set map[Feature]bool
+
+	// CPUImplementer is part of the processor signature.
+	CPUImplementer uint8
+
+	// CPUArchitecture is part of the processor signature.
+	CPUArchitecture uint8
+
+	// CPUVariant is part of the processor signature.
+	CPUVariant uint8
+
+	// CPUPartnum is part of the processor signature.
+	CPUPartnum uint16
+
+	// CPURevision is part of the processor signature.
+	CPURevision uint8
+}
+
+// CheckHostCompatible returns nil if fs is a subset of the host feature set.
+// Noop on arm64.
+func (fs *FeatureSet) CheckHostCompatible() error {
+	return nil
+}
+
+// ExtendedStateSize returns the number of bytes needed to save the "extended
+// state" for this processor and the boundary it must be aligned to. Extended
+// state includes floating point(NEON) registers, and other cpu state that's not
+// associated with the normal task context.
+func (fs *FeatureSet) ExtendedStateSize() (size, align uint) {
+	// ARMv8 provide 32x128bits NEON registers.
+	//
+	// Ref arch/arm64/include/uapi/asm/ptrace.h
+	// struct user_fpsimd_state {
+	//        __uint128_t     vregs[32];
+	//        __u32           fpsr;
+	//	  __u32           fpcr;
+	//	  __u32           __reserved[2];
+	// };
+	return 528, 16
+}
+
+// HasFeature tests whether or not a feature is in the given feature set.
+func (fs *FeatureSet) HasFeature(feature Feature) bool {
+	return fs.Set[feature]
+}
+
+// UseXsave returns true if 'fs' supports the "xsave" instruction.
+//
+// Irrelevant on arm64.
+func (fs *FeatureSet) UseXsave() bool {
+	return false
+}
+
+// FlagsString prints out supported CPU "flags" field in /proc/cpuinfo.
+func (fs *FeatureSet) FlagsString() string {
+	var s []string
+	for f, _ := range arm64FeatureStrings {
+		if fs.Set[f] {
+			if fstr := f.flagString(); fstr != "" {
+				s = append(s, fstr)
+			}
+		}
+	}
+	return strings.Join(s, " ")
+}
+
+// WriteCPUInfoTo is to generate a section of one cpu in /proc/cpuinfo. This is
+// a minimal /proc/cpuinfo, and the bogomips field is simply made up.
+func (fs FeatureSet) WriteCPUInfoTo(cpu uint, b *bytes.Buffer) {
+	fmt.Fprintf(b, "processor\t: %d\n", cpu)
+	fmt.Fprintf(b, "BogoMIPS\t: %.02f\n", cpuFreqMHz) // It's bogus anyway.
+	fmt.Fprintf(b, "Features\t\t: %s\n", fs.FlagsString())
+	fmt.Fprintf(b, "CPU implementer\t: 0x%x\n", cpuImplHex)
+	fmt.Fprintf(b, "CPU architecture\t: %d\n", cpuArchDec)
+	fmt.Fprintf(b, "CPU variant\t: 0x%x\n", cpuVarHex)
+	fmt.Fprintf(b, "CPU part\t: 0x%x\n", cpuPartHex)
+	fmt.Fprintf(b, "CPU revision\t: %d\n", cpuRevDec)
+	fmt.Fprintln(b, "") // The /proc/cpuinfo file ends with an extra newline.
+}
+
+// HostFeatureSet uses hwCap to get host values and construct a feature set
+// that matches that of the host machine.
+func HostFeatureSet() *FeatureSet {
+	s := make(map[Feature]bool)
+
+	for f, _ := range arm64FeatureStrings {
+		if hwCap&(1<<f) != 0 {
+			s[f] = true
+		}
+	}
+
+	return &FeatureSet{
+		Set:             s,
+		CPUImplementer:  uint8(cpuImplHex),
+		CPUArchitecture: uint8(cpuArchDec),
+		CPUVariant:      uint8(cpuVarHex),
+		CPUPartnum:      uint16(cpuPartHex),
+		CPURevision:     uint8(cpuRevDec),
+	}
+}
+
+// Reads bogomips from host /proc/cpuinfo. Must run before whitelisting.
+// This value is used to create the fake /proc/cpuinfo from a FeatureSet.
+func initCPUInfo() {
+	cpuinfob, err := ioutil.ReadFile("/proc/cpuinfo")
+	if err != nil {
+		// Leave it as 0. The standalone VDSO bails out in the same way.
+		log.Warningf("Could not read /proc/cpuinfo: %v", err)
+		return
+	}
+	cpuinfo := string(cpuinfob)
+
+	// We get the value straight from host /proc/cpuinfo.
+	for _, line := range strings.Split(cpuinfo, "\n") {
+		switch {
+		case strings.Contains(line, "BogoMIPS"):
+			{
+				splitMHz := strings.Split(line, ":")
+				if len(splitMHz) < 2 {
+					log.Warningf("Could not read /proc/cpuinfo: malformed BogoMIPS")
+					break
+				}
+
+				// If there was a problem, leave cpuFreqMHz as 0.
+				var err error
+				cpuFreqMHz, err = strconv.ParseFloat(strings.TrimSpace(splitMHz[1]), 64)
+				if err != nil {
+					log.Warningf("Could not parse BogoMIPS value %v: %v", splitMHz[1], err)
+					cpuFreqMHz = 0
+				}
+			}
+		case strings.Contains(line, "CPU implementer"):
+			{
+				splitImpl := strings.Split(line, ":")
+				if len(splitImpl) < 2 {
+					log.Warningf("Could not read /proc/cpuinfo: malformed CPU implementer")
+					break
+				}
+
+				// If there was a problem, leave cpuImplHex as 0.
+				var err error
+				cpuImplHex, err = strconv.ParseUint(strings.TrimSpace(splitImpl[1]), 0, 64)
+				if err != nil {
+					log.Warningf("Could not parse CPU implementer value %v: %v", splitImpl[1], err)
+					cpuImplHex = 0
+				}
+			}
+		case strings.Contains(line, "CPU architecture"):
+			{
+				splitArch := strings.Split(line, ":")
+				if len(splitArch) < 2 {
+					log.Warningf("Could not read /proc/cpuinfo: malformed CPU architecture")
+					break
+				}
+
+				// If there was a problem, leave cpuArchDec as 0.
+				var err error
+				cpuArchDec, err = strconv.ParseUint(strings.TrimSpace(splitArch[1]), 0, 64)
+				if err != nil {
+					log.Warningf("Could not parse CPU architecture value %v: %v", splitArch[1], err)
+					cpuArchDec = 0
+				}
+			}
+		case strings.Contains(line, "CPU variant"):
+			{
+				splitVar := strings.Split(line, ":")
+				if len(splitVar) < 2 {
+					log.Warningf("Could not read /proc/cpuinfo: malformed CPU variant")
+					break
+				}
+
+				// If there was a problem, leave cpuVarHex as 0.
+				var err error
+				cpuVarHex, err = strconv.ParseUint(strings.TrimSpace(splitVar[1]), 0, 64)
+				if err != nil {
+					log.Warningf("Could not parse CPU variant value %v: %v", splitVar[1], err)
+					cpuVarHex = 0
+				}
+			}
+		case strings.Contains(line, "CPU part"):
+			{
+				splitPart := strings.Split(line, ":")
+				if len(splitPart) < 2 {
+					log.Warningf("Could not read /proc/cpuinfo: malformed CPU part")
+					break
+				}
+
+				// If there was a problem, leave cpuPartHex as 0.
+				var err error
+				cpuPartHex, err = strconv.ParseUint(strings.TrimSpace(splitPart[1]), 0, 64)
+				if err != nil {
+					log.Warningf("Could not parse CPU part value %v: %v", splitPart[1], err)
+					cpuPartHex = 0
+				}
+			}
+		case strings.Contains(line, "CPU revision"):
+			{
+				splitRev := strings.Split(line, ":")
+				if len(splitRev) < 2 {
+					log.Warningf("Could not read /proc/cpuinfo: malformed CPU revision")
+					break
+				}
+
+				// If there was a problem, leave cpuRevDec as 0.
+				var err error
+				cpuRevDec, err = strconv.ParseUint(strings.TrimSpace(splitRev[1]), 0, 64)
+				if err != nil {
+					log.Warningf("Could not parse CPU revision value %v: %v", splitRev[1], err)
+					cpuRevDec = 0
+				}
+			}
+		}
+	}
+}
+
+// The auxiliary vector of a process on the Linux system can be read
+// from /proc/self/auxv, and tags and values are stored as 8-bytes
+// decimal key-value pairs on the 64-bit system.
+//
+// $ od -t d8 /proc/self/auxv
+//  0000000                   33      140734615224320
+//  0000020                   16           3219913727
+//  0000040                    6                 4096
+//  0000060                   17                  100
+//  0000100                    3       94665627353152
+//  0000120                    4                   56
+//  0000140                    5                    9
+//  0000160                    7      140425502162944
+//  0000200                    8                    0
+//  0000220                    9       94665627365760
+//  0000240                   11                 1000
+//  0000260                   12                 1000
+//  0000300                   13                 1000
+//  0000320                   14                 1000
+//  0000340                   23                    0
+//  0000360                   25      140734614619513
+//  0000400                   26                    0
+//  0000420                   31      140734614626284
+//  0000440                   15      140734614619529
+//  0000460                    0                    0
+func initHwCap() {
+	auxv, err := ioutil.ReadFile("/proc/self/auxv")
+	if err != nil {
+		log.Warningf("Could not read /proc/self/auxv: %v", err)
+		return
+	}
+
+	l := len(auxv) / 16
+	for i := 0; i < l; i++ {
+		tag := binary.LittleEndian.Uint64(auxv[i*16:])
+		val := binary.LittleEndian.Uint64(auxv[(i*16 + 8):])
+		if tag == _AT_HWCAP {
+			hwCap = uint(val)
+			break
+		}
+	}
+}
+
+func initFeaturesFromString() {
+	for f, s := range arm64FeatureStrings {
+		arm64FeaturesFromString[s] = f
+	}
+}
+
+func init() {
+	initCPUInfo()
+	initHwCap()
+	initFeaturesFromString()
+}
diff --git a/pkg/cpuid/cpuid_arm64_test.go b/pkg/cpuid/cpuid_arm64_test.go
new file mode 100644
index 000000000..a34f67779
--- /dev/null
+++ b/pkg/cpuid/cpuid_arm64_test.go
@@ -0,0 +1,55 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build arm64
+
+package cpuid
+
+import (
+	"testing"
+)
+
+var justFP = &FeatureSet{
+	Set: map[Feature]bool{
+		ARM64FeatureFP: true,
+	}}
+
+func TestHostFeatureSet(t *testing.T) {
+	hostFeatures := HostFeatureSet()
+	if len(hostFeatures.Set) == 0 {
+		t.Errorf("Got invalid feature set %v from HostFeatureSet()", hostFeatures)
+	}
+}
+
+func TestHasFeature(t *testing.T) {
+	if !justFP.HasFeature(ARM64FeatureFP) {
+		t.Errorf("HasFeature failed, %v should contain %v", justFP, ARM64FeatureFP)
+	}
+
+	if justFP.HasFeature(ARM64FeatureSM3) {
+		t.Errorf("HasFeature failed, %v should not contain %v", justFP, ARM64FeatureSM3)
+	}
+}
+
+func TestFeatureFromString(t *testing.T) {
+	f, ok := FeatureFromString("asimd")
+	if f != ARM64FeatureASIMD || !ok {
+		t.Errorf("got %v want asimd", f)
+	}
+
+	f, ok = FeatureFromString("bad")
+	if ok {
+		t.Errorf("got %v want nothing", f)
+	}
+}
diff --git a/pkg/cpuid/cpuid_parse_test.go b/pkg/cpuid/cpuid_parse_x86_test.go
index dd9969db4..d48418e69 100644
--- a/pkg/cpuid/cpuid_parse_test.go
+++ b/pkg/cpuid/cpuid_parse_x86_test.go
@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build i386 amd64
+
 package cpuid
 
 import (
diff --git a/pkg/cpuid/cpuid_x86.go b/pkg/cpuid/cpuid_x86.go
new file mode 100644
index 000000000..333ca0a04
--- /dev/null
+++ b/pkg/cpuid/cpuid_x86.go
@@ -0,0 +1,1100 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build i386 amd64
+
+package cpuid
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"strconv"
+	"strings"
+
+	"gvisor.dev/gvisor/pkg/log"
+)
+
+// Common references for CPUID leaves and bits:
+//
+// Intel:
+//   * Intel SDM Volume 2, Chapter 3.2 "CPUID" (more up-to-date)
+//   * Intel Application Note 485 (more detailed)
+//
+// AMD:
+//   * AMD64 APM Volume 3, Appendix 3 "Obtaining Processor Information ..."
+
+// block is a collection of 32 Feature bits.
+type block int
+
+const blockSize = 32
+
+// Feature bits are numbered according to "blocks". Each block is 32 bits, and
+// feature bits from the same source (cpuid leaf/level) are in the same block.
+func featureID(b block, bit int) Feature {
+	return Feature(32*int(b) + bit)
+}
+
+// Block 0 constants are all of the "basic" feature bits returned by a cpuid in
+// ecx with eax=1.
+const (
+	X86FeatureSSE3 Feature = iota
+	X86FeaturePCLMULDQ
+	X86FeatureDTES64
+	X86FeatureMONITOR
+	X86FeatureDSCPL
+	X86FeatureVMX
+	X86FeatureSMX
+	X86FeatureEST
+	X86FeatureTM2
+	X86FeatureSSSE3 // Not a typo, "supplemental" SSE3.
+	X86FeatureCNXTID
+	X86FeatureSDBG
+	X86FeatureFMA
+	X86FeatureCX16
+	X86FeatureXTPR
+	X86FeaturePDCM
+	_ // ecx bit 16 is reserved.
+	X86FeaturePCID
+	X86FeatureDCA
+	X86FeatureSSE4_1
+	X86FeatureSSE4_2
+	X86FeatureX2APIC
+	X86FeatureMOVBE
+	X86FeaturePOPCNT
+	X86FeatureTSCD
+	X86FeatureAES
+	X86FeatureXSAVE
+	X86FeatureOSXSAVE
+	X86FeatureAVX
+	X86FeatureF16C
+	X86FeatureRDRAND
+	_ // ecx bit 31 is reserved.
+)
+
+// Block 1 constants are all of the "basic" feature bits returned by a cpuid in
+// edx with eax=1.
+const (
+	X86FeatureFPU Feature = 32 + iota
+	X86FeatureVME
+	X86FeatureDE
+	X86FeaturePSE
+	X86FeatureTSC
+	X86FeatureMSR
+	X86FeaturePAE
+	X86FeatureMCE
+	X86FeatureCX8
+	X86FeatureAPIC
+	_ // edx bit 10 is reserved.
+	X86FeatureSEP
+	X86FeatureMTRR
+	X86FeaturePGE
+	X86FeatureMCA
+	X86FeatureCMOV
+	X86FeaturePAT
+	X86FeaturePSE36
+	X86FeaturePSN
+	X86FeatureCLFSH
+	_ // edx bit 20 is reserved.
+	X86FeatureDS
+	X86FeatureACPI
+	X86FeatureMMX
+	X86FeatureFXSR
+	X86FeatureSSE
+	X86FeatureSSE2
+	X86FeatureSS
+	X86FeatureHTT
+	X86FeatureTM
+	X86FeatureIA64
+	X86FeaturePBE
+)
+
+// Block 2 bits are the "structured extended" features returned in ebx for
+// eax=7, ecx=0.
+const (
+	X86FeatureFSGSBase Feature = 2*32 + iota
+	X86FeatureTSC_ADJUST
+	_ // ebx bit 2 is reserved.
+	X86FeatureBMI1
+	X86FeatureHLE
+	X86FeatureAVX2
+	X86FeatureFDP_EXCPTN_ONLY
+	X86FeatureSMEP
+	X86FeatureBMI2
+	X86FeatureERMS
+	X86FeatureINVPCID
+	X86FeatureRTM
+	X86FeatureCQM
+	X86FeatureFPCSDS
+	X86FeatureMPX
+	X86FeatureRDT
+	X86FeatureAVX512F
+	X86FeatureAVX512DQ
+	X86FeatureRDSEED
+	X86FeatureADX
+	X86FeatureSMAP
+	X86FeatureAVX512IFMA
+	X86FeaturePCOMMIT
+	X86FeatureCLFLUSHOPT
+	X86FeatureCLWB
+	X86FeatureIPT // Intel processor trace.
+	X86FeatureAVX512PF
+	X86FeatureAVX512ER
+	X86FeatureAVX512CD
+	X86FeatureSHA
+	X86FeatureAVX512BW
+	X86FeatureAVX512VL
+)
+
+// Block 3 bits are the "extended" features returned in ecx for eax=7, ecx=0.
+const (
+	X86FeaturePREFETCHWT1 Feature = 3*32 + iota
+	X86FeatureAVX512VBMI
+	X86FeatureUMIP
+	X86FeaturePKU
+	X86FeatureOSPKE
+	X86FeatureWAITPKG
+	X86FeatureAVX512_VBMI2
+	_ // ecx bit 7 is reserved
+	X86FeatureGFNI
+	X86FeatureVAES
+	X86FeatureVPCLMULQDQ
+	X86FeatureAVX512_VNNI
+	X86FeatureAVX512_BITALG
+	X86FeatureTME
+	X86FeatureAVX512_VPOPCNTDQ
+	_ // ecx bit 15 is reserved
+	X86FeatureLA57
+	// ecx bits 17-21 are reserved
+	_
+	_
+	_
+	_
+	_
+	X86FeatureRDPID
+	// ecx bits 23-24 are reserved
+	_
+	_
+	X86FeatureCLDEMOTE
+	_ // ecx bit 26 is reserved
+	X86FeatureMOVDIRI
+	X86FeatureMOVDIR64B
+)
+
+// Block 4 constants are for xsave capabilities in CPUID.(EAX=0DH,ECX=01H):EAX.
+// The CPUID leaf is available only if 'X86FeatureXSAVE' is present.
+const (
+	X86FeatureXSAVEOPT Feature = 4*32 + iota
+	X86FeatureXSAVEC
+	X86FeatureXGETBV1
+	X86FeatureXSAVES
+	// EAX[31:4] are reserved.
+)
+
+// Block 5 constants are the extended feature bits in
+// CPUID.(EAX=0x80000001):ECX.
+const (
+	X86FeatureLAHF64 Feature = 5*32 + iota
+	X86FeatureCMP_LEGACY
+	X86FeatureSVM
+	X86FeatureEXTAPIC
+	X86FeatureCR8_LEGACY
+	X86FeatureLZCNT
+	X86FeatureSSE4A
+	X86FeatureMISALIGNSSE
+	X86FeaturePREFETCHW
+	X86FeatureOSVW
+	X86FeatureIBS
+	X86FeatureXOP
+	X86FeatureSKINIT
+	X86FeatureWDT
+	_ // ecx bit 14 is reserved.
+	X86FeatureLWP
+	X86FeatureFMA4
+	X86FeatureTCE
+	_ // ecx bit 18 is reserved.
+	_ // ecx bit 19 is reserved.
+	_ // ecx bit 20 is reserved.
+	X86FeatureTBM
+	X86FeatureTOPOLOGY
+	X86FeaturePERFCTR_CORE
+	X86FeaturePERFCTR_NB
+	_ // ecx bit 25 is reserved.
+	X86FeatureBPEXT
+	X86FeaturePERFCTR_TSC
+	X86FeaturePERFCTR_LLC
+	X86FeatureMWAITX
+	// ECX[31:30] are reserved.
+)
+
+// Block 6 constants are the extended feature bits in
+// CPUID.(EAX=0x80000001):EDX.
+//
+// These are sparse, and so the bit positions are assigned manually.
+const (
+	// On AMD, EDX[24:23] | EDX[17:12] | EDX[9:0] are duplicate features
+	// also defined in block 1 (in identical bit positions). Those features
+	// are not listed here.
+	block6DuplicateMask = 0x183f3ff
+
+	X86FeatureSYSCALL  Feature = 6*32 + 11
+	X86FeatureNX       Feature = 6*32 + 20
+	X86FeatureMMXEXT   Feature = 6*32 + 22
+	X86FeatureFXSR_OPT Feature = 6*32 + 25
+	X86FeatureGBPAGES  Feature = 6*32 + 26
+	X86FeatureRDTSCP   Feature = 6*32 + 27
+	X86FeatureLM       Feature = 6*32 + 29
+	X86Feature3DNOWEXT Feature = 6*32 + 30
+	X86Feature3DNOW    Feature = 6*32 + 31
+)
+
+// linuxBlockOrder defines the order in which linux organizes the feature
+// blocks. Linux also tracks feature bits in 32-bit blocks, but in an order
+// which doesn't match well here, so for the /proc/cpuinfo generation we simply
+// re-map the blocks to Linux's ordering and then go through the bits in each
+// block.
+var linuxBlockOrder = []block{1, 6, 0, 5, 2, 4, 3}
+
+// To make emulation of /proc/cpuinfo easy, these names match the names of the
+// basic features in Linux defined in arch/x86/kernel/cpu/capflags.c.
+var x86FeatureStrings = map[Feature]string{
+	// Block 0.
+	X86FeatureSSE3:     "pni",
+	X86FeaturePCLMULDQ: "pclmulqdq",
+	X86FeatureDTES64:   "dtes64",
+	X86FeatureMONITOR:  "monitor",
+	X86FeatureDSCPL:    "ds_cpl",
+	X86FeatureVMX:      "vmx",
+	X86FeatureSMX:      "smx",
+	X86FeatureEST:      "est",
+	X86FeatureTM2:      "tm2",
+	X86FeatureSSSE3:    "ssse3",
+	X86FeatureCNXTID:   "cid",
+	X86FeatureSDBG:     "sdbg",
+	X86FeatureFMA:      "fma",
+	X86FeatureCX16:     "cx16",
+	X86FeatureXTPR:     "xtpr",
+	X86FeaturePDCM:     "pdcm",
+	X86FeaturePCID:     "pcid",
+	X86FeatureDCA:      "dca",
+	X86FeatureSSE4_1:   "sse4_1",
+	X86FeatureSSE4_2:   "sse4_2",
+	X86FeatureX2APIC:   "x2apic",
+	X86FeatureMOVBE:    "movbe",
+	X86FeaturePOPCNT:   "popcnt",
+	X86FeatureTSCD:     "tsc_deadline_timer",
+	X86FeatureAES:      "aes",
+	X86FeatureXSAVE:    "xsave",
+	X86FeatureAVX:      "avx",
+	X86FeatureF16C:     "f16c",
+	X86FeatureRDRAND:   "rdrand",
+
+	// Block 1.
+	X86FeatureFPU:   "fpu",
+	X86FeatureVME:   "vme",
+	X86FeatureDE:    "de",
+	X86FeaturePSE:   "pse",
+	X86FeatureTSC:   "tsc",
+	X86FeatureMSR:   "msr",
+	X86FeaturePAE:   "pae",
+	X86FeatureMCE:   "mce",
+	X86FeatureCX8:   "cx8",
+	X86FeatureAPIC:  "apic",
+	X86FeatureSEP:   "sep",
+	X86FeatureMTRR:  "mtrr",
+	X86FeaturePGE:   "pge",
+	X86FeatureMCA:   "mca",
+	X86FeatureCMOV:  "cmov",
+	X86FeaturePAT:   "pat",
+	X86FeaturePSE36: "pse36",
+	X86FeaturePSN:   "pn",
+	X86FeatureCLFSH: "clflush",
+	X86FeatureDS:    "dts",
+	X86FeatureACPI:  "acpi",
+	X86FeatureMMX:   "mmx",
+	X86FeatureFXSR:  "fxsr",
+	X86FeatureSSE:   "sse",
+	X86FeatureSSE2:  "sse2",
+	X86FeatureSS:    "ss",
+	X86FeatureHTT:   "ht",
+	X86FeatureTM:    "tm",
+	X86FeatureIA64:  "ia64",
+	X86FeaturePBE:   "pbe",
+
+	// Block 2.
+	X86FeatureFSGSBase:   "fsgsbase",
+	X86FeatureTSC_ADJUST: "tsc_adjust",
+	X86FeatureBMI1:       "bmi1",
+	X86FeatureHLE:        "hle",
+	X86FeatureAVX2:       "avx2",
+	X86FeatureSMEP:       "smep",
+	X86FeatureBMI2:       "bmi2",
+	X86FeatureERMS:       "erms",
+	X86FeatureINVPCID:    "invpcid",
+	X86FeatureRTM:        "rtm",
+	X86FeatureCQM:        "cqm",
+	X86FeatureMPX:        "mpx",
+	X86FeatureRDT:        "rdt_a",
+	X86FeatureAVX512F:    "avx512f",
+	X86FeatureAVX512DQ:   "avx512dq",
+	X86FeatureRDSEED:     "rdseed",
+	X86FeatureADX:        "adx",
+	X86FeatureSMAP:       "smap",
+	X86FeatureCLWB:       "clwb",
+	X86FeatureAVX512PF:   "avx512pf",
+	X86FeatureAVX512ER:   "avx512er",
+	X86FeatureAVX512CD:   "avx512cd",
+	X86FeatureSHA:        "sha_ni",
+	X86FeatureAVX512BW:   "avx512bw",
+	X86FeatureAVX512VL:   "avx512vl",
+
+	// Block 3.
+	X86FeatureAVX512VBMI:       "avx512vbmi",
+	X86FeatureUMIP:             "umip",
+	X86FeaturePKU:              "pku",
+	X86FeatureOSPKE:            "ospke",
+	X86FeatureWAITPKG:          "waitpkg",
+	X86FeatureAVX512_VBMI2:     "avx512_vbmi2",
+	X86FeatureGFNI:             "gfni",
+	X86FeatureVAES:             "vaes",
+	X86FeatureVPCLMULQDQ:       "vpclmulqdq",
+	X86FeatureAVX512_VNNI:      "avx512_vnni",
+	X86FeatureAVX512_BITALG:    "avx512_bitalg",
+	X86FeatureTME:              "tme",
+	X86FeatureAVX512_VPOPCNTDQ: "avx512_vpopcntdq",
+	X86FeatureLA57:             "la57",
+	X86FeatureRDPID:            "rdpid",
+	X86FeatureCLDEMOTE:         "cldemote",
+	X86FeatureMOVDIRI:          "movdiri",
+	X86FeatureMOVDIR64B:        "movdir64b",
+
+	// Block 4.
+	X86FeatureXSAVEOPT: "xsaveopt",
+	X86FeatureXSAVEC:   "xsavec",
+	X86FeatureXGETBV1:  "xgetbv1",
+	X86FeatureXSAVES:   "xsaves",
+
+	// Block 5.
+	X86FeatureLAHF64:       "lahf_lm", // LAHF/SAHF in long mode
+	X86FeatureCMP_LEGACY:   "cmp_legacy",
+	X86FeatureSVM:          "svm",
+	X86FeatureEXTAPIC:      "extapic",
+	X86FeatureCR8_LEGACY:   "cr8_legacy",
+	X86FeatureLZCNT:        "abm", // Advanced bit manipulation
+	X86FeatureSSE4A:        "sse4a",
+	X86FeatureMISALIGNSSE:  "misalignsse",
+	X86FeaturePREFETCHW:    "3dnowprefetch",
+	X86FeatureOSVW:         "osvw",
+	X86FeatureIBS:          "ibs",
+	X86FeatureXOP:          "xop",
+	X86FeatureSKINIT:       "skinit",
+	X86FeatureWDT:          "wdt",
+	X86FeatureLWP:          "lwp",
+	X86FeatureFMA4:         "fma4",
+	X86FeatureTCE:          "tce",
+	X86FeatureTBM:          "tbm",
+	X86FeatureTOPOLOGY:     "topoext",
+	X86FeaturePERFCTR_CORE: "perfctr_core",
+	X86FeaturePERFCTR_NB:   "perfctr_nb",
+	X86FeatureBPEXT:        "bpext",
+	X86FeaturePERFCTR_TSC:  "ptsc",
+	X86FeaturePERFCTR_LLC:  "perfctr_llc",
+	X86FeatureMWAITX:       "mwaitx",
+
+	// Block 6.
+	X86FeatureSYSCALL:  "syscall",
+	X86FeatureNX:       "nx",
+	X86FeatureMMXEXT:   "mmxext",
+	X86FeatureFXSR_OPT: "fxsr_opt",
+	X86FeatureGBPAGES:  "pdpe1gb",
+	X86FeatureRDTSCP:   "rdtscp",
+	X86FeatureLM:       "lm",
+	X86Feature3DNOWEXT: "3dnowext",
+	X86Feature3DNOW:    "3dnow",
+}
+
+// These flags are parse only---they can be used for setting / unsetting the
+// flags, but will not get printed out in /proc/cpuinfo.
+var x86FeatureParseOnlyStrings = map[Feature]string{
+	// Block 0.
+	X86FeatureOSXSAVE: "osxsave",
+
+	// Block 2.
+	X86FeatureFDP_EXCPTN_ONLY: "fdp_excptn_only",
+	X86FeatureFPCSDS:          "fpcsds",
+	X86FeatureIPT:             "pt",
+	X86FeatureCLFLUSHOPT:      "clfushopt",
+
+	// Block 3.
+	X86FeaturePREFETCHWT1: "prefetchwt1",
+}
+
+// intelCacheDescriptors describe the caches and TLBs on the system. They are
+// returned in the registers for eax=2. Intel only.
+type intelCacheDescriptor uint8
+
+// Valid cache/TLB descriptors. All descriptors can be found in Intel SDM Vol.
+// 2, Ch. 3.2, "CPUID", Table 3-12 "Encoding of CPUID Leaf 2 Descriptors".
+const (
+	intelNullDescriptor    intelCacheDescriptor = 0
+	intelNoTLBDescriptor   intelCacheDescriptor = 0xfe
+	intelNoCacheDescriptor intelCacheDescriptor = 0xff
+
+	// Most descriptors omitted for brevity as they are currently unused.
+)
+
+// CacheType describes the type of a cache, as returned in eax[4:0] for eax=4.
+type CacheType uint8
+
+const (
+	// cacheNull indicates that there are no more entries.
+	cacheNull CacheType = iota
+
+	// CacheData is a data cache.
+	CacheData
+
+	// CacheInstruction is an instruction cache.
+	CacheInstruction
+
+	// CacheUnified is a unified instruction and data cache.
+	CacheUnified
+)
+
+// Cache describes the parameters of a single cache on the system.
+//
+// +stateify savable
+type Cache struct {
+	// Level is the hierarchical level of this cache (L1, L2, etc).
+	Level uint32
+
+	// Type is the type of cache.
+	Type CacheType
+
+	// FullyAssociative indicates that entries may be placed in any block.
+	FullyAssociative bool
+
+	// Partitions is the number of physical partitions in the cache.
+	Partitions uint32
+
+	// Ways is the number of ways of associativity in the cache.
+	Ways uint32
+
+	// Sets is the number of sets in the cache.
+	Sets uint32
+
+	// InvalidateHierarchical indicates that WBINVD/INVD from threads
+	// sharing this cache acts upon lower level caches for threads sharing
+	// this cache.
+	InvalidateHierarchical bool
+
+	// Inclusive indicates that this cache is inclusive of lower cache
+	// levels.
+	Inclusive bool
+
+	// DirectMapped indicates that this cache is directly mapped from
+	// address, rather than using a hash function.
+	DirectMapped bool
+}
+
+// Just a way to wrap cpuid function numbers.
+type cpuidFunction uint32
+
+// The constants below are the lower or "standard" cpuid functions, ordered as
+// defined by the hardware.
+const (
+	vendorID                      cpuidFunction = iota // Returns vendor ID and largest standard function.
+	featureInfo                                        // Returns basic feature bits and processor signature.
+	intelCacheDescriptors                              // Returns list of cache descriptors. Intel only.
+	intelSerialNumber                                  // Returns processor serial number (obsolete on new hardware). Intel only.
+	intelDeterministicCacheParams                      // Returns deterministic cache information. Intel only.
+	monitorMwaitParams                                 // Returns information about monitor/mwait instructions.
+	powerParams                                        // Returns information about power management and thermal sensors.
+	extendedFeatureInfo                                // Returns extended feature bits.
+	_                                                  // Function 0x8 is reserved.
+	intelDCAParams                                     // Returns direct cache access information. Intel only.
+	intelPMCInfo                                       // Returns information about performance monitoring features. Intel only.
+	intelX2APICInfo                                    // Returns core/logical processor topology. Intel only.
+	_                                                  // Function 0xc is reserved.
+	xSaveInfo                                          // Returns information about extended state management.
+)
+
+// The "extended" functions start at 0x80000000.
+const (
+	extendedFunctionInfo cpuidFunction = 0x80000000 + iota // Returns highest available extended function in eax.
+	extendedFeatures                                       // Returns some extended feature bits in edx and ecx.
+)
+
+// These are the extended floating point state features. They are used to
+// enumerate floating point features in XCR0, XSTATE_BV, etc.
+const (
+	XSAVEFeatureX87         = 1 << 0
+	XSAVEFeatureSSE         = 1 << 1
+	XSAVEFeatureAVX         = 1 << 2
+	XSAVEFeatureBNDREGS     = 1 << 3
+	XSAVEFeatureBNDCSR      = 1 << 4
+	XSAVEFeatureAVX512op    = 1 << 5
+	XSAVEFeatureAVX512zmm0  = 1 << 6
+	XSAVEFeatureAVX512zmm16 = 1 << 7
+	XSAVEFeaturePKRU        = 1 << 9
+)
+
+var cpuFreqMHz float64
+
+// x86FeaturesFromString includes features from x86FeatureStrings and
+// x86FeatureParseOnlyStrings.
+var x86FeaturesFromString = make(map[string]Feature)
+
+// FeatureFromString returns the Feature associated with the given feature
+// string plus a bool to indicate if it could find the feature.
+func FeatureFromString(s string) (Feature, bool) {
+	f, b := x86FeaturesFromString[s]
+	return f, b
+}
+
+// String implements fmt.Stringer.
+func (f Feature) String() string {
+	if s := f.flagString(false); s != "" {
+		return s
+	}
+
+	block := int(f) / 32
+	bit := int(f) % 32
+	return fmt.Sprintf("<cpuflag %d; block %d bit %d>", f, block, bit)
+}
+
+func (f Feature) flagString(cpuinfoOnly bool) string {
+	if s, ok := x86FeatureStrings[f]; ok {
+		return s
+	}
+	if !cpuinfoOnly {
+		return x86FeatureParseOnlyStrings[f]
+	}
+	return ""
+}
+
+// FeatureSet is a set of Features for a CPU.
+//
+// +stateify savable
+type FeatureSet struct {
+	// Set is the set of features that are enabled in this FeatureSet.
+	Set map[Feature]bool
+
+	// VendorID is the 12-char string returned in ebx:edx:ecx for eax=0.
+	VendorID string
+
+	// ExtendedFamily is part of the processor signature.
+	ExtendedFamily uint8
+
+	// ExtendedModel is part of the processor signature.
+	ExtendedModel uint8
+
+	// ProcessorType is part of the processor signature.
+	ProcessorType uint8
+
+	// Family is part of the processor signature.
+	Family uint8
+
+	// Model is part of the processor signature.
+	Model uint8
+
+	// SteppingID is part of the processor signature.
+	SteppingID uint8
+
+	// Caches describes the caches on the CPU.
+	Caches []Cache
+
+	// CacheLine is the size of a cache line in bytes.
+	//
+	// All caches use the same line size. This is not enforced in the CPUID
+	// encoding, but is true on all known x86 processors.
+	CacheLine uint32
+}
+
+// FlagsString prints out supported CPU flags. If cpuinfoOnly is true, it is
+// equivalent to the "flags" field in /proc/cpuinfo.
+func (fs *FeatureSet) FlagsString(cpuinfoOnly bool) string {
+	var s []string
+	for _, b := range linuxBlockOrder {
+		for i := 0; i < blockSize; i++ {
+			if f := featureID(b, i); fs.Set[f] {
+				if fstr := f.flagString(cpuinfoOnly); fstr != "" {
+					s = append(s, fstr)
+				}
+			}
+		}
+	}
+	return strings.Join(s, " ")
+}
+
+// WriteCPUInfoTo is to generate a section of one cpu in /proc/cpuinfo. This is
+// a minimal /proc/cpuinfo, it is missing some fields like "microcode" that are
+// not always printed in Linux. The bogomips field is simply made up.
+func (fs FeatureSet) WriteCPUInfoTo(cpu uint, b *bytes.Buffer) {
+	fmt.Fprintf(b, "processor\t: %d\n", cpu)
+	fmt.Fprintf(b, "vendor_id\t: %s\n", fs.VendorID)
+	fmt.Fprintf(b, "cpu family\t: %d\n", ((fs.ExtendedFamily<<4)&0xff)|fs.Family)
+	fmt.Fprintf(b, "model\t\t: %d\n", ((fs.ExtendedModel<<4)&0xff)|fs.Model)
+	fmt.Fprintf(b, "model name\t: %s\n", "unknown") // Unknown for now.
+	fmt.Fprintf(b, "stepping\t: %s\n", "unknown")   // Unknown for now.
+	fmt.Fprintf(b, "cpu MHz\t\t: %.3f\n", cpuFreqMHz)
+	fmt.Fprintln(b, "fpu\t\t: yes")
+	fmt.Fprintln(b, "fpu_exception\t: yes")
+	fmt.Fprintf(b, "cpuid level\t: %d\n", uint32(xSaveInfo)) // Same as ax in vendorID.
+	fmt.Fprintln(b, "wp\t\t: yes")
+	fmt.Fprintf(b, "flags\t\t: %s\n", fs.FlagsString(true))
+	fmt.Fprintf(b, "bogomips\t: %.02f\n", cpuFreqMHz) // It's bogus anyway.
+	fmt.Fprintf(b, "clflush size\t: %d\n", fs.CacheLine)
+	fmt.Fprintf(b, "cache_alignment\t: %d\n", fs.CacheLine)
+	fmt.Fprintf(b, "address sizes\t: %d bits physical, %d bits virtual\n", 46, 48)
+	fmt.Fprintln(b, "power management:") // This is always here, but can be blank.
+	fmt.Fprintln(b, "")                  // The /proc/cpuinfo file ends with an extra newline.
+}
+
+const (
+	amdVendorID   = "AuthenticAMD"
+	intelVendorID = "GenuineIntel"
+)
+
+// AMD returns true if fs describes an AMD CPU.
+func (fs *FeatureSet) AMD() bool {
+	return fs.VendorID == amdVendorID
+}
+
+// Intel returns true if fs describes an Intel CPU.
+func (fs *FeatureSet) Intel() bool {
+	return fs.VendorID == intelVendorID
+}
+
+// ErrIncompatible is returned by FeatureSet.HostCompatible if fs is not a
+// subset of the host feature set.
+type ErrIncompatible struct {
+	message string
+}
+
+// Error implements error.
+func (e ErrIncompatible) Error() string {
+	return e.message
+}
+
+// CheckHostCompatible returns nil if fs is a subset of the host feature set.
+func (fs *FeatureSet) CheckHostCompatible() error {
+	hfs := HostFeatureSet()
+
+	if diff := fs.Subtract(hfs); diff != nil {
+		return ErrIncompatible{fmt.Sprintf("CPU feature set %v incompatible with host feature set %v (missing: %v)", fs.FlagsString(false), hfs.FlagsString(false), diff)}
+	}
+
+	// The size of a cache line must match, as it is critical to correctly
+	// utilizing CLFLUSH. Other cache properties are allowed to change, as
+	// they are not important to correctness.
+	if fs.CacheLine != hfs.CacheLine {
+		return ErrIncompatible{fmt.Sprintf("CPU cache line size %d incompatible with host cache line size %d", fs.CacheLine, hfs.CacheLine)}
+	}
+
+	return nil
+}
+
+// Helper to convert 3 regs into 12-byte vendor ID.
+func vendorIDFromRegs(bx, cx, dx uint32) string {
+	bytes := make([]byte, 0, 12)
+	for i := uint(0); i < 4; i++ {
+		b := byte(bx >> (i * 8))
+		bytes = append(bytes, b)
+	}
+
+	for i := uint(0); i < 4; i++ {
+		b := byte(dx >> (i * 8))
+		bytes = append(bytes, b)
+	}
+
+	for i := uint(0); i < 4; i++ {
+		b := byte(cx >> (i * 8))
+		bytes = append(bytes, b)
+	}
+	return string(bytes)
+}
+
+// ExtendedStateSize returns the number of bytes needed to save the "extended
+// state" for this processor and the boundary it must be aligned to. Extended
+// state includes floating point registers, and other cpu state that's not
+// associated with the normal task context.
+//
+// Note: We can save some space here with an optimization where we use a
+// smaller chunk of memory depending on features that are actually enabled.
+// Currently we just use the largest possible size for simplicity (which is
+// about 2.5K worst case, with avx512).
+func (fs *FeatureSet) ExtendedStateSize() (size, align uint) {
+	if fs.UseXsave() {
+		// Leaf 0 of xsaveinfo function returns the size for currently
+		// enabled xsave features in ebx, the maximum size if all valid
+		// features are saved with xsave in ecx, and valid XCR0 bits in
+		// edx:eax.
+		_, _, maxSize, _ := HostID(uint32(xSaveInfo), 0)
+		return uint(maxSize), 64
+	}
+
+	// If we don't support xsave, we fall back to fxsave, which requires
+	// 512 bytes aligned to 16 bytes.
+	return 512, 16
+}
+
+// ValidXCR0Mask returns the bits that may be set to 1 in control register
+// XCR0.
+func (fs *FeatureSet) ValidXCR0Mask() uint64 {
+	if !fs.UseXsave() {
+		return 0
+	}
+	eax, _, _, edx := HostID(uint32(xSaveInfo), 0)
+	return uint64(edx)<<32 | uint64(eax)
+}
+
+// vendorIDRegs returns the 3 register values used to construct the 12-byte
+// vendor ID string for eax=0.
+func (fs *FeatureSet) vendorIDRegs() (bx, dx, cx uint32) {
+	for i := uint(0); i < 4; i++ {
+		bx |= uint32(fs.VendorID[i]) << (i * 8)
+	}
+
+	for i := uint(0); i < 4; i++ {
+		dx |= uint32(fs.VendorID[i+4]) << (i * 8)
+	}
+
+	for i := uint(0); i < 4; i++ {
+		cx |= uint32(fs.VendorID[i+8]) << (i * 8)
+	}
+	return
+}
+
+// signature returns the signature dword that's returned in eax when eax=1.
+func (fs *FeatureSet) signature() uint32 {
+	var s uint32
+	s |= uint32(fs.SteppingID & 0xf)
+	s |= uint32(fs.Model&0xf) << 4
+	s |= uint32(fs.Family&0xf) << 8
+	s |= uint32(fs.ProcessorType&0x3) << 12
+	s |= uint32(fs.ExtendedModel&0xf) << 16
+	s |= uint32(fs.ExtendedFamily&0xff) << 20
+	return s
+}
+
+// Helper to deconstruct signature dword.
+func signatureSplit(v uint32) (ef, em, pt, f, m, sid uint8) {
+	sid = uint8(v & 0xf)
+	m = uint8(v>>4) & 0xf
+	f = uint8(v>>8) & 0xf
+	pt = uint8(v>>12) & 0x3
+	em = uint8(v>>16) & 0xf
+	ef = uint8(v >> 20)
+	return
+}
+
+// Helper to convert blockwise feature bit masks into a set of features. Masks
+// must be provided in order for each block, without skipping them. If a block
+// does not matter for this feature set, 0 is specified.
+func setFromBlockMasks(blocks ...uint32) map[Feature]bool {
+	s := make(map[Feature]bool)
+	for b, blockMask := range blocks {
+		for i := 0; i < blockSize; i++ {
+			if blockMask&1 != 0 {
+				s[featureID(block(b), i)] = true
+			}
+			blockMask >>= 1
+		}
+	}
+	return s
+}
+
+// blockMask returns the 32-bit mask associated with a block of features.
+func (fs *FeatureSet) blockMask(b block) uint32 {
+	var mask uint32
+	for i := 0; i < blockSize; i++ {
+		if fs.Set[featureID(b, i)] {
+			mask |= 1 << uint(i)
+		}
+	}
+	return mask
+}
+
+// Remove removes a Feature from a FeatureSet. It ignores features
+// that are not in the FeatureSet.
+func (fs *FeatureSet) Remove(feature Feature) {
+	delete(fs.Set, feature)
+}
+
+// Add adds a Feature to a FeatureSet. It ignores duplicate features.
+func (fs *FeatureSet) Add(feature Feature) {
+	fs.Set[feature] = true
+}
+
+// HasFeature tests whether or not a feature is in the given feature set.
+func (fs *FeatureSet) HasFeature(feature Feature) bool {
+	return fs.Set[feature]
+}
+
+// Subtract returns the features present in fs that are not present in other.
+// If all features in fs are present in other, Subtract returns nil.
+func (fs *FeatureSet) Subtract(other *FeatureSet) (diff map[Feature]bool) {
+	for f := range fs.Set {
+		if !other.Set[f] {
+			if diff == nil {
+				diff = make(map[Feature]bool)
+			}
+			diff[f] = true
+		}
+	}
+
+	return
+}
+
+// EmulateID emulates a cpuid instruction based on the feature set.
+func (fs *FeatureSet) EmulateID(origAx, origCx uint32) (ax, bx, cx, dx uint32) {
+	switch cpuidFunction(origAx) {
+	case vendorID:
+		ax = uint32(xSaveInfo) // 0xd (xSaveInfo) is the highest function we support.
+		bx, dx, cx = fs.vendorIDRegs()
+	case featureInfo:
+		// CLFLUSH line size is encoded in quadwords. Other fields in bx unsupported.
+		bx = (fs.CacheLine / 8) << 8
+		cx = fs.blockMask(block(0))
+		dx = fs.blockMask(block(1))
+		ax = fs.signature()
+	case intelCacheDescriptors:
+		if !fs.Intel() {
+			// Reserved on non-Intel.
+			return 0, 0, 0, 0
+		}
+
+		// "The least-significant byte in register EAX (register AL)
+		// will always return 01H. Software should ignore this value
+		// and not interpret it as an informational descriptor." - SDM
+		//
+		// We only support reporting cache parameters via
+		// intelDeterministicCacheParams; report as much here.
+		//
+		// We do not support exposing TLB information at all.
+		ax = 1 | (uint32(intelNoCacheDescriptor) << 8)
+	case intelDeterministicCacheParams:
+		if !fs.Intel() {
+			// Reserved on non-Intel.
+			return 0, 0, 0, 0
+		}
+
+		// cx is the index of the cache to describe.
+		if int(origCx) >= len(fs.Caches) {
+			return uint32(cacheNull), 0, 0, 0
+		}
+		c := fs.Caches[origCx]
+
+		ax = uint32(c.Type)
+		ax |= c.Level << 5
+		ax |= 1 << 8 // Always claim the cache is "self-initializing".
+		if c.FullyAssociative {
+			ax |= 1 << 9
+		}
+		// Processor topology not supported.
+
+		bx = fs.CacheLine - 1
+		bx |= (c.Partitions - 1) << 12
+		bx |= (c.Ways - 1) << 22
+
+		cx = c.Sets - 1
+
+		if !c.InvalidateHierarchical {
+			dx |= 1
+		}
+		if c.Inclusive {
+			dx |= 1 << 1
+		}
+		if !c.DirectMapped {
+			dx |= 1 << 2
+		}
+	case xSaveInfo:
+		if !fs.UseXsave() {
+			return 0, 0, 0, 0
+		}
+		return HostID(uint32(xSaveInfo), origCx)
+	case extendedFeatureInfo:
+		if origCx != 0 {
+			break // Only leaf 0 is supported.
+		}
+		bx = fs.blockMask(block(2))
+		cx = fs.blockMask(block(3))
+	case extendedFunctionInfo:
+		// We only support showing the extended features.
+		ax = uint32(extendedFeatures)
+		cx = 0
+	case extendedFeatures:
+		cx = fs.blockMask(block(5))
+		dx = fs.blockMask(block(6))
+		if fs.AMD() {
+			// AMD duplicates some block 1 features in block 6.
+			dx |= fs.blockMask(block(1)) & block6DuplicateMask
+		}
+	}
+
+	return
+}
+
+// UseXsave returns the choice of fp state saving instruction.
+func (fs *FeatureSet) UseXsave() bool {
+	return fs.HasFeature(X86FeatureXSAVE) && fs.HasFeature(X86FeatureOSXSAVE)
+}
+
+// UseXsaveopt returns true if 'fs' supports the "xsaveopt" instruction.
+func (fs *FeatureSet) UseXsaveopt() bool {
+	return fs.UseXsave() && fs.HasFeature(X86FeatureXSAVEOPT)
+}
+
+// HostID executes a native CPUID instruction.
+func HostID(axArg, cxArg uint32) (ax, bx, cx, dx uint32)
+
+// HostFeatureSet uses cpuid to get host values and construct a feature set
+// that matches that of the host machine. Note that there are several places
+// where there appear to be some unnecessary assignments between register names
+// (ax, bx, cx, or dx) and featureBlockN variables. This is to explicitly show
+// where the different feature blocks come from, to make the code easier to
+// inspect and read.
+func HostFeatureSet() *FeatureSet {
+	// eax=0 gets max supported feature and vendor ID.
+	_, bx, cx, dx := HostID(0, 0)
+	vendorID := vendorIDFromRegs(bx, cx, dx)
+
+	// eax=1 gets basic features in ecx:edx.
+	ax, bx, cx, dx := HostID(1, 0)
+	featureBlock0 := cx
+	featureBlock1 := dx
+	ef, em, pt, f, m, sid := signatureSplit(ax)
+	cacheLine := 8 * (bx >> 8) & 0xff
+
+	// eax=4, ecx=i gets details about cache index i. Only supported on Intel.
+	var caches []Cache
+	if vendorID == intelVendorID {
+		// ecx selects the cache index until a null type is returned.
+		for i := uint32(0); ; i++ {
+			ax, bx, cx, dx := HostID(4, i)
+			t := CacheType(ax & 0xf)
+			if t == cacheNull {
+				break
+			}
+
+			lineSize := (bx & 0xfff) + 1
+			if lineSize != cacheLine {
+				panic(fmt.Sprintf("Mismatched cache line size: %d vs %d", lineSize, cacheLine))
+			}
+
+			caches = append(caches, Cache{
+				Type:                   t,
+				Level:                  (ax >> 5) & 0x7,
+				FullyAssociative:       ((ax >> 9) & 1) == 1,
+				Partitions:             ((bx >> 12) & 0x3ff) + 1,
+				Ways:                   ((bx >> 22) & 0x3ff) + 1,
+				Sets:                   cx + 1,
+				InvalidateHierarchical: (dx & 1) == 0,
+				Inclusive:              ((dx >> 1) & 1) == 1,
+				DirectMapped:           ((dx >> 2) & 1) == 0,
+			})
+		}
+	}
+
+	// eax=7, ecx=0 gets extended features in ecx:ebx.
+	_, bx, cx, _ = HostID(7, 0)
+	featureBlock2 := bx
+	featureBlock3 := cx
+
+	// Leaf 0xd is supported only if CPUID.1:ECX.XSAVE[bit 26] is set.
+	var featureBlock4 uint32
+	if (featureBlock0 & (1 << 26)) != 0 {
+		featureBlock4, _, _, _ = HostID(uint32(xSaveInfo), 1)
+	}
+
+	// eax=0x80000000 gets supported extended levels. We use this to
+	// determine if there are any non-zero block 4 or block 6 bits to find.
+	var featureBlock5, featureBlock6 uint32
+	if ax, _, _, _ := HostID(uint32(extendedFunctionInfo), 0); ax >= uint32(extendedFeatures) {
+		// eax=0x80000001 gets AMD added feature bits.
+		_, _, cx, dx = HostID(uint32(extendedFeatures), 0)
+		featureBlock5 = cx
+		// Ignore features duplicated from block 1 on AMD. These bits
+		// are reserved on Intel.
+		featureBlock6 = dx &^ block6DuplicateMask
+	}
+
+	set := setFromBlockMasks(featureBlock0, featureBlock1, featureBlock2, featureBlock3, featureBlock4, featureBlock5, featureBlock6)
+	return &FeatureSet{
+		Set:            set,
+		VendorID:       vendorID,
+		ExtendedFamily: ef,
+		ExtendedModel:  em,
+		ProcessorType:  pt,
+		Family:         f,
+		Model:          m,
+		SteppingID:     sid,
+		CacheLine:      cacheLine,
+		Caches:         caches,
+	}
+}
+
+// Reads max cpu frequency from host /proc/cpuinfo. Must run before
+// whitelisting. This value is used to create the fake /proc/cpuinfo from a
+// FeatureSet.
+func initCPUFreq() {
+	cpuinfob, err := ioutil.ReadFile("/proc/cpuinfo")
+	if err != nil {
+		// Leave it as 0... The standalone VDSO bails out in the same
+		// way.
+		log.Warningf("Could not read /proc/cpuinfo: %v", err)
+		return
+	}
+	cpuinfo := string(cpuinfob)
+
+	// We get the value straight from host /proc/cpuinfo. On machines with
+	// frequency scaling enabled, this will only get the current value
+	// which will likely be inaccurate. This is fine on machines with
+	// frequency scaling disabled.
+	for _, line := range strings.Split(cpuinfo, "\n") {
+		if strings.Contains(line, "cpu MHz") {
+			splitMHz := strings.Split(line, ":")
+			if len(splitMHz) < 2 {
+				log.Warningf("Could not read /proc/cpuinfo: malformed cpu MHz line")
+				return
+			}
+
+			// If there was a problem, leave cpuFreqMHz as 0.
+			var err error
+			cpuFreqMHz, err = strconv.ParseFloat(strings.TrimSpace(splitMHz[1]), 64)
+			if err != nil {
+				log.Warningf("Could not parse cpu MHz value %v: %v", splitMHz[1], err)
+				cpuFreqMHz = 0
+				return
+			}
+			return
+		}
+	}
+	log.Warningf("Could not parse /proc/cpuinfo, it is empty or does not contain cpu MHz")
+}
+
+func initFeaturesFromString() {
+	for f, s := range x86FeatureStrings {
+		x86FeaturesFromString[s] = f
+	}
+	for f, s := range x86FeatureParseOnlyStrings {
+		x86FeaturesFromString[s] = f
+	}
+}
+
+func init() {
+	// initCpuFreq must be run before whitelists are enabled.
+	initCPUFreq()
+	initFeaturesFromString()
+}
diff --git a/pkg/cpuid/cpuid_test.go b/pkg/cpuid/cpuid_x86_test.go
index a707ebb55..0fe20c213 100644
--- a/pkg/cpuid/cpuid_test.go
+++ b/pkg/cpuid/cpuid_x86_test.go
@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build i386 amd64
+
 package cpuid
 
 import (