From a534b2c65236201703096bb010f8d6b742f14c0d Mon Sep 17 00:00:00 2001 From: Bin Lu Date: Fri, 15 May 2020 05:28:46 -0400 Subject: adding the VM-Exit method for Arm64 On amd64, it uses 'HLT' to leave the guest. Unlike amd64, arm64 can only uses mmio_exit/psci to leave the guest. So, I designed the HYPERCALL_VMEXIT to be compatible with amd64/arm64. To keep it simple, I used the address of exception table as the MMIO base address, so that I can trigger a MMIO-EXIT by forcibly writing this space. Then, in host user space, I can calculate this address to find out which hypercall. Signed-off-by: Bin Lu --- pkg/sentry/platform/kvm/bluepill_amd64_unsafe.go | 7 +++++ pkg/sentry/platform/kvm/bluepill_arm64_unsafe.go | 13 ++++++++ pkg/sentry/platform/kvm/bluepill_unsafe.go | 39 ++++++++++++++++-------- pkg/sentry/platform/kvm/kvm_arm64.go | 3 ++ pkg/sentry/platform/kvm/kvm_const.go | 10 ++++++ pkg/sentry/platform/kvm/kvm_const_arm64.go | 7 +++++ pkg/sentry/platform/kvm/machine_arm64_unsafe.go | 4 +++ 7 files changed, 70 insertions(+), 13 deletions(-) (limited to 'pkg/sentry/platform/kvm') diff --git a/pkg/sentry/platform/kvm/bluepill_amd64_unsafe.go b/pkg/sentry/platform/kvm/bluepill_amd64_unsafe.go index 99cac665d..0d1e83e6c 100644 --- a/pkg/sentry/platform/kvm/bluepill_amd64_unsafe.go +++ b/pkg/sentry/platform/kvm/bluepill_amd64_unsafe.go @@ -53,3 +53,10 @@ func dieArchSetup(c *vCPU, context *arch.SignalContext64, guestRegs *userRegs) { context.Rbx = uint64(uintptr(unsafe.Pointer(c))) context.Rip = uint64(dieTrampolineAddr) } + +// getHypercallID returns hypercall ID. +// +//go:nosplit +func getHypercallID(addr uintptr) int { + return _KVM_HYPERCALL_MAX +} diff --git a/pkg/sentry/platform/kvm/bluepill_arm64_unsafe.go b/pkg/sentry/platform/kvm/bluepill_arm64_unsafe.go index 4ca2b7717..abd36f973 100644 --- a/pkg/sentry/platform/kvm/bluepill_arm64_unsafe.go +++ b/pkg/sentry/platform/kvm/bluepill_arm64_unsafe.go @@ -61,3 +61,16 @@ func dieArchSetup(c *vCPU, context *arch.SignalContext64, guestRegs *userRegs) { func bluepillArchFpContext(context unsafe.Pointer) *arch.FpsimdContext { return &((*arch.SignalContext64)(context).Fpsimd64) } + +// getHypercallID returns hypercall ID. +// +// On Arm64, the MMIO address should be 64-bit aligned. +// +//go:nosplit +func getHypercallID(addr uintptr) int { + if addr < arm64HypercallMMIOBase || addr >= (arm64HypercallMMIOBase+_AARCH64_HYPERCALL_MMIO_SIZE) { + return _KVM_HYPERCALL_MAX + } else { + return int(((addr) - arm64HypercallMMIOBase) >> 3) + } +} diff --git a/pkg/sentry/platform/kvm/bluepill_unsafe.go b/pkg/sentry/platform/kvm/bluepill_unsafe.go index 9add7c944..e79097b5d 100644 --- a/pkg/sentry/platform/kvm/bluepill_unsafe.go +++ b/pkg/sentry/platform/kvm/bluepill_unsafe.go @@ -58,6 +58,24 @@ func bluepillArchContext(context unsafe.Pointer) *arch.SignalContext64 { return &((*arch.UContext64)(context).MContext) } +// bluepillHandleHlt is reponsible for handling VM-Exit. +// +//go:nosplit +func bluepillGuestExit(c *vCPU, context unsafe.Pointer) { + // Copy out registers. + bluepillArchExit(c, bluepillArchContext(context)) + + // Return to the vCPUReady state; notify any waiters. + user := atomic.LoadUint32(&c.state) & vCPUUser + switch atomic.SwapUint32(&c.state, user) { + case user | vCPUGuest: // Expected case. + case user | vCPUGuest | vCPUWaiter: + c.notify() + default: + throw("invalid state") + } +} + // bluepillHandler is called from the signal stub. // // The world may be stopped while this is executing, and it executes on the @@ -156,25 +174,20 @@ func bluepillHandler(context unsafe.Pointer) { c.die(bluepillArchContext(context), "debug") return case _KVM_EXIT_HLT: - // Copy out registers. - bluepillArchExit(c, bluepillArchContext(context)) - - // Return to the vCPUReady state; notify any waiters. - user := atomic.LoadUint32(&c.state) & vCPUUser - switch atomic.SwapUint32(&c.state, user) { - case user | vCPUGuest: // Expected case. - case user | vCPUGuest | vCPUWaiter: - c.notify() - default: - throw("invalid state") - } + bluepillGuestExit(c, context) return case _KVM_EXIT_MMIO: + physical := uintptr(c.runData.data[0]) + if getHypercallID(physical) == _KVM_HYPERCALL_VMEXIT { + bluepillGuestExit(c, context) + return + } + // Increment the fault count. atomic.AddUint32(&c.faults, 1) // For MMIO, the physical address is the first data item. - physical := uintptr(c.runData.data[0]) + physical = uintptr(c.runData.data[0]) virtual, ok := handleBluepillFault(c.machine, physical, physicalRegions, _KVM_MEM_FLAGS_NONE) if !ok { c.die(bluepillArchContext(context), "invalid physical address") diff --git a/pkg/sentry/platform/kvm/kvm_arm64.go b/pkg/sentry/platform/kvm/kvm_arm64.go index 29d457a7e..3134a076b 100644 --- a/pkg/sentry/platform/kvm/kvm_arm64.go +++ b/pkg/sentry/platform/kvm/kvm_arm64.go @@ -26,6 +26,9 @@ type kvmOneReg struct { addr uint64 } +// arm64HypercallMMIOBase is MMIO base address used to dispatch hypercalls. +var arm64HypercallMMIOBase uintptr + const KVM_NR_SPSR = 5 type userFpsimdState struct { diff --git a/pkg/sentry/platform/kvm/kvm_const.go b/pkg/sentry/platform/kvm/kvm_const.go index 1d5c77ff4..6a7676468 100644 --- a/pkg/sentry/platform/kvm/kvm_const.go +++ b/pkg/sentry/platform/kvm/kvm_const.go @@ -71,3 +71,13 @@ const ( _KVM_MEM_READONLY = uint32(1) << 1 _KVM_MEM_FLAGS_NONE = 0 ) + +// KVM hypercall list. +// Canonical list of hypercalls supported. +const ( + // On amd64, it uses 'HLT' to leave the guest. + // Unlike amd64, arm64 can only uses mmio_exit/psci to leave the guest. + // _KVM_HYPERCALL_VMEXIT is only used on Arm64 for now. + _KVM_HYPERCALL_VMEXIT int = iota + _KVM_HYPERCALL_MAX +) diff --git a/pkg/sentry/platform/kvm/kvm_const_arm64.go b/pkg/sentry/platform/kvm/kvm_const_arm64.go index 531ae8b1e..6f0539c29 100644 --- a/pkg/sentry/platform/kvm/kvm_const_arm64.go +++ b/pkg/sentry/platform/kvm/kvm_const_arm64.go @@ -131,3 +131,10 @@ const ( _ESR_SEGV_PEMERR_L2 = 0xe _ESR_SEGV_PEMERR_L3 = 0xf ) + +// Arm64: MMIO base address used to dispatch hypercalls. +const ( + // on Arm64, the MMIO address must be 64-bit aligned. + // Currently, we only need 1 hypercall: hypercall_vmexit. + _AARCH64_HYPERCALL_MMIO_SIZE = 1 << 3 +) diff --git a/pkg/sentry/platform/kvm/machine_arm64_unsafe.go b/pkg/sentry/platform/kvm/machine_arm64_unsafe.go index 3c02cef7c..48c834499 100644 --- a/pkg/sentry/platform/kvm/machine_arm64_unsafe.go +++ b/pkg/sentry/platform/kvm/machine_arm64_unsafe.go @@ -159,6 +159,10 @@ func (c *vCPU) initArchState() error { return err } + // Use the address of the exception vector table as + // the MMIO address base. + arm64HypercallMMIOBase = toLocation + data = ring0.PsrDefaultSet | ring0.KernelFlagsSet reg.id = _KVM_ARM64_REGS_PSTATE if err := c.setOneRegister(®); err != nil { -- cgit v1.2.3