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// Copyright 2018 Google Inc.
//
// 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 amd64
package kvm
import (
"fmt"
"syscall"
"unsafe"
"gvisor.googlesource.com/gvisor/pkg/sentry/platform/ring0/pagetables"
)
var (
runDataSize int
hasGuestPCID bool
pagetablesOpts pagetables.Opts
cpuidSupported = cpuidEntries{nr: _KVM_NR_CPUID_ENTRIES}
)
func updateSystemValues(fd int) error {
// Extract the mmap size.
sz, _, errno := syscall.RawSyscall(syscall.SYS_IOCTL, uintptr(fd), _KVM_GET_VCPU_MMAP_SIZE, 0)
if errno != 0 {
return fmt.Errorf("getting VCPU mmap size: %v", errno)
}
// Save the data.
runDataSize = int(sz)
// Must do the dance to figure out the number of entries.
_, _, errno = syscall.RawSyscall(
syscall.SYS_IOCTL,
uintptr(fd),
_KVM_GET_SUPPORTED_CPUID,
uintptr(unsafe.Pointer(&cpuidSupported)))
if errno != 0 && errno != syscall.ENOMEM {
// Some other error occurred.
return fmt.Errorf("getting supported CPUID: %v", errno)
}
// The number should now be correct.
_, _, errno = syscall.RawSyscall(
syscall.SYS_IOCTL,
uintptr(fd),
_KVM_GET_SUPPORTED_CPUID,
uintptr(unsafe.Pointer(&cpuidSupported)))
if errno != 0 {
// Didn't work with the right number.
return fmt.Errorf("getting supported CPUID (2nd attempt): %v", errno)
}
// Calculate whether guestPCID is supported.
//
// FIXME: These should go through the much more pleasant
// cpuid package interfaces, once a way to accept raw kvm CPUID entries
// is plumbed (or some rough equivalent).
for i := 0; i < int(cpuidSupported.nr); i++ {
entry := cpuidSupported.entries[i]
if entry.function == 1 && entry.index == 0 && entry.ecx&(1<<17) != 0 {
hasGuestPCID = true // Found matching PCID in guest feature set.
}
}
// Set the pagetables to use PCID if it's available.
pagetablesOpts.EnablePCID = hasGuestPCID
// Success.
return nil
}
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