github.com/metacubex/gvisor@v0.0.0-20240320004321-933faba989ec/pkg/sentry/platform/kvm/context.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  package kvm
    16  
    17  import (
    18  	"github.com/metacubex/gvisor/pkg/abi/linux"
    19  	pkgcontext "github.com/metacubex/gvisor/pkg/context"
    20  	"github.com/metacubex/gvisor/pkg/hostarch"
    21  	"github.com/metacubex/gvisor/pkg/ring0"
    22  	"github.com/metacubex/gvisor/pkg/sentry/arch"
    23  	"github.com/metacubex/gvisor/pkg/sentry/platform"
    24  	"github.com/metacubex/gvisor/pkg/sentry/platform/interrupt"
    25  )
    26  
    27  // platformContext is an implementation of the platform context.
    28  //
    29  // This is a thin wrapper around the machine.
    30  type platformContext struct {
    31  	// machine is the parent machine, and is immutable.
    32  	machine *machine
    33  
    34  	// info is the linux.SignalInfo cached for this platformContext.
    35  	info linux.SignalInfo
    36  
    37  	// interrupt is the interrupt platformContext.
    38  	interrupt interrupt.Forwarder
    39  }
    40  
    41  // tryCPUIDError indicates that CPUID emulation should occur.
    42  type tryCPUIDError struct{}
    43  
    44  // Error implements error.Error.
    45  func (tryCPUIDError) Error() string { return "cpuid emulation failed" }
    46  
    47  // Switch runs the provided platformContext in the given address space.
    48  func (c *platformContext) Switch(ctx pkgcontext.Context, mm platform.MemoryManager, ac *arch.Context64, _ int32) (*linux.SignalInfo, hostarch.AccessType, error) {
    49  	as := mm.AddressSpace()
    50  	localAS := as.(*addressSpace)
    51  
    52  restart:
    53  	// Grab a vCPU.
    54  	cpu := c.machine.Get()
    55  
    56  	// Enable interrupts (i.e. calls to vCPU.Notify).
    57  	if !c.interrupt.Enable(cpu) {
    58  		c.machine.Put(cpu) // Already preempted.
    59  		return nil, hostarch.NoAccess, platform.ErrContextInterrupt
    60  	}
    61  
    62  	// Set the active address space.
    63  	//
    64  	// This must be done prior to the call to Touch below. If the address
    65  	// space is invalidated between this line and the call below, we will
    66  	// flag on entry anyways. When the active address space below is
    67  	// cleared, it indicates that we don't need an explicit interrupt and
    68  	// that the flush can occur naturally on the next user entry.
    69  	cpu.active.set(localAS)
    70  
    71  	// Prepare switch options.
    72  	switchOpts := ring0.SwitchOpts{
    73  		Registers:          &ac.StateData().Regs,
    74  		FloatingPointState: ac.FloatingPointData(),
    75  		PageTables:         localAS.pageTables,
    76  		Flush:              localAS.Touch(cpu),
    77  		FullRestore:        ac.FullRestore(),
    78  	}
    79  
    80  	// Take the blue pill.
    81  	at, err := cpu.SwitchToUser(switchOpts, &c.info)
    82  
    83  	// Clear the address space.
    84  	cpu.active.set(nil)
    85  
    86  	// Increment the number of user exits.
    87  	cpu.userExits.Add(1)
    88  	userExitCounter.Increment()
    89  
    90  	// Release resources.
    91  	c.machine.Put(cpu)
    92  
    93  	// All done.
    94  	c.interrupt.Disable()
    95  
    96  	if err != nil {
    97  		if _, ok := err.(tryCPUIDError); ok {
    98  			// Does emulation work for the CPUID?
    99  			//
   100  			// We have to put the current vCPU, because
   101  			// TryCPUIDEmulate needs to read a user memory and it
   102  			// has to lock mm.activeMu for that, but it can race
   103  			// with as.invalidate that bonce all vcpu-s to gr0 and
   104  			// is called under mm.activeMu too.
   105  			if platform.TryCPUIDEmulate(ctx, mm, ac) {
   106  				goto restart
   107  			}
   108  			// If not a valid CPUID, then the signal should be
   109  			// delivered as is and the information is filled.
   110  			err = platform.ErrContextSignal
   111  		}
   112  	}
   113  	return &c.info, at, err
   114  }
   115  
   116  // Interrupt interrupts the running context.
   117  func (c *platformContext) Interrupt() {
   118  	c.interrupt.NotifyInterrupt()
   119  }
   120  
   121  // Release implements platform.Context.Release().
   122  func (c *platformContext) Release() {}
   123  
   124  // FullStateChanged implements platform.Context.FullStateChanged.
   125  func (c *platformContext) FullStateChanged() {}
   126  
   127  // PullFullState implements platform.Context.PullFullState.
   128  func (c *platformContext) PullFullState(as platform.AddressSpace, ac *arch.Context64) error {
   129  	return nil
   130  }
   131  
   132  // PrepareSleep implements platform.Context.platform.Context.
   133  func (*platformContext) PrepareSleep() {}