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// Copyright 2018 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.
// Package kvm provides a kvm-based implementation of the platform interface.
package kvm
import (
"fmt"
"os"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/hostarch"
"gvisor.dev/gvisor/pkg/ring0"
"gvisor.dev/gvisor/pkg/ring0/pagetables"
"gvisor.dev/gvisor/pkg/sentry/platform"
"gvisor.dev/gvisor/pkg/sync"
)
// userMemoryRegion is a region of physical memory.
//
// This mirrors kvm_memory_region.
type userMemoryRegion struct {
slot uint32
flags uint32
guestPhysAddr uint64
memorySize uint64
userspaceAddr uint64
}
// runData is the run structure. This may be mapped for synchronous register
// access (although that doesn't appear to be supported by my kernel at least).
//
// This mirrors kvm_run.
type runData struct {
requestInterruptWindow uint8
_ [7]uint8
exitReason uint32
readyForInterruptInjection uint8
ifFlag uint8
_ [2]uint8
cr8 uint64
apicBase uint64
// This is the union data for exits. Interpretation depends entirely on
// the exitReason above (see vCPU code for more information).
data [32]uint64
}
// KVM represents a lightweight VM context.
type KVM struct {
platform.NoCPUPreemptionDetection
// KVM never changes mm_structs.
platform.UseHostProcessMemoryBarrier
// machine is the backing VM.
machine *machine
}
var (
globalOnce sync.Once
globalErr error
)
// OpenDevice opens the KVM device at /dev/kvm and returns the File.
func OpenDevice() (*os.File, error) {
dev, ok := os.LookupEnv("GVISOR_KVM_DEV")
if !ok {
dev = "/dev/kvm"
}
f, err := os.OpenFile(dev, unix.O_RDWR, 0)
if err != nil {
return nil, fmt.Errorf("error opening /dev/kvm: %v", err)
}
return f, nil
}
// New returns a new KVM-based implementation of the platform interface.
func New(deviceFile *os.File) (*KVM, error) {
fd := deviceFile.Fd()
// Ensure global initialization is done.
globalOnce.Do(func() {
globalErr = updateGlobalOnce(int(fd))
})
if globalErr != nil {
return nil, globalErr
}
// Create a new VM fd.
var (
vm uintptr
errno unix.Errno
)
for {
vm, _, errno = unix.Syscall(unix.SYS_IOCTL, fd, _KVM_CREATE_VM, 0)
if errno == unix.EINTR {
continue
}
if errno != 0 {
return nil, fmt.Errorf("creating VM: %v", errno)
}
break
}
// We are done with the device file.
deviceFile.Close()
// Create a VM context.
machine, err := newMachine(int(vm))
if err != nil {
return nil, err
}
// All set.
return &KVM{
machine: machine,
}, nil
}
// SupportsAddressSpaceIO implements platform.Platform.SupportsAddressSpaceIO.
func (*KVM) SupportsAddressSpaceIO() bool {
return false
}
// CooperativelySchedulesAddressSpace implements platform.Platform.CooperativelySchedulesAddressSpace.
func (*KVM) CooperativelySchedulesAddressSpace() bool {
return false
}
// MapUnit implements platform.Platform.MapUnit.
func (*KVM) MapUnit() uint64 {
// We greedily creates PTEs in MapFile, so extremely large mappings can
// be expensive. Not _that_ expensive since we allow super pages, but
// even though can get out of hand if you're creating multi-terabyte
// mappings. For this reason, we limit mappings to an arbitrary 16MB.
return 16 << 20
}
// MinUserAddress returns the lowest available address.
func (*KVM) MinUserAddress() hostarch.Addr {
return hostarch.PageSize
}
// MaxUserAddress returns the first address that may not be used.
func (*KVM) MaxUserAddress() hostarch.Addr {
return hostarch.Addr(ring0.MaximumUserAddress)
}
// NewAddressSpace returns a new pagetable root.
func (k *KVM) NewAddressSpace(_ interface{}) (platform.AddressSpace, <-chan struct{}, error) {
// Allocate page tables and install system mappings.
pageTables := pagetables.NewWithUpper(newAllocator(), k.machine.upperSharedPageTables, ring0.KernelStartAddress)
// Return the new address space.
return &addressSpace{
machine: k.machine,
pageTables: pageTables,
dirtySet: k.machine.newDirtySet(),
}, nil, nil
}
// NewContext returns an interruptible context.
func (k *KVM) NewContext() platform.Context {
return &context{
machine: k.machine,
}
}
type constructor struct{}
func (*constructor) New(f *os.File) (platform.Platform, error) {
return New(f)
}
func (*constructor) OpenDevice() (*os.File, error) {
return OpenDevice()
}
// Flags implements platform.Constructor.Flags().
func (*constructor) Requirements() platform.Requirements {
return platform.Requirements{}
}
func init() {
platform.Register("kvm", &constructor{})
}
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