github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sentry/platform/kvm/kvm_amd64_unsafe.go (about)

     1  // Copyright 2018 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // +build amd64
    16  
    17  package kvm
    18  
    19  import (
    20  	"fmt"
    21  	"unsafe"
    22  
    23  	"golang.org/x/sys/unix"
    24  )
    25  
    26  var (
    27  	runDataSize    int
    28  	hasGuestPCID   bool
    29  	cpuidSupported = cpuidEntries{nr: _KVM_NR_CPUID_ENTRIES}
    30  )
    31  
    32  func updateSystemValues(fd int) error {
    33  	// Extract the mmap size.
    34  	sz, _, errno := unix.RawSyscall(unix.SYS_IOCTL, uintptr(fd), _KVM_GET_VCPU_MMAP_SIZE, 0)
    35  	if errno != 0 {
    36  		return fmt.Errorf("getting VCPU mmap size: %v", errno)
    37  	}
    38  
    39  	// Save the data.
    40  	runDataSize = int(sz)
    41  
    42  	// Must do the dance to figure out the number of entries.
    43  	_, _, errno = unix.RawSyscall(
    44  		unix.SYS_IOCTL,
    45  		uintptr(fd),
    46  		_KVM_GET_SUPPORTED_CPUID,
    47  		uintptr(unsafe.Pointer(&cpuidSupported)))
    48  	if errno != 0 && errno != unix.ENOMEM {
    49  		// Some other error occurred.
    50  		return fmt.Errorf("getting supported CPUID: %v", errno)
    51  	}
    52  
    53  	// The number should now be correct.
    54  	_, _, errno = unix.RawSyscall(
    55  		unix.SYS_IOCTL,
    56  		uintptr(fd),
    57  		_KVM_GET_SUPPORTED_CPUID,
    58  		uintptr(unsafe.Pointer(&cpuidSupported)))
    59  	if errno != 0 {
    60  		// Didn't work with the right number.
    61  		return fmt.Errorf("getting supported CPUID (2nd attempt): %v", errno)
    62  	}
    63  
    64  	// Calculate whether guestPCID is supported.
    65  	//
    66  	// FIXME(ascannell): These should go through the much more pleasant
    67  	// cpuid package interfaces, once a way to accept raw kvm CPUID entries
    68  	// is plumbed (or some rough equivalent).
    69  	for i := 0; i < int(cpuidSupported.nr); i++ {
    70  		entry := cpuidSupported.entries[i]
    71  		if entry.function == 1 && entry.index == 0 && entry.ecx&(1<<17) != 0 {
    72  			hasGuestPCID = true // Found matching PCID in guest feature set.
    73  		}
    74  	}
    75  
    76  	// Success.
    77  	return nil
    78  }