Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 81 insertions, 0 deletions

diff --git a/pkg/sentry/platform/kvm/context.go b/pkg/sentry/platform/kvm/context.go
new file mode 100644
index 000000000..fd04a2c47
--- /dev/null
+++ b/pkg/sentry/platform/kvm/context.go
@@ -0,0 +1,81 @@
+// 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.
+
+package kvm
+
+import (
+	"sync/atomic"
+
+	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/platform/interrupt"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/platform/ring0"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+// context is an implementation of the platform context.
+//
+// This is a thin wrapper around the machine.
+type context struct {
+	// machine is the parent machine, and is immutable.
+	machine *machine
+
+	// interrupt is the interrupt context.
+	interrupt interrupt.Forwarder
+}
+
+// Switch runs the provided context in the given address space.
+func (c *context) Switch(as platform.AddressSpace, ac arch.Context, _ int32) (*arch.SignalInfo, usermem.AccessType, error) {
+	// Extract data.
+	localAS := as.(*addressSpace)
+	regs := &ac.StateData().Regs
+	fp := (*byte)(ac.FloatingPointData())
+
+	// Grab a vCPU.
+	cpu, err := c.machine.Get()
+	if err != nil {
+		return nil, usermem.NoAccess, err
+	}
+
+	// Enable interrupts (i.e. calls to vCPU.Notify).
+	if !c.interrupt.Enable(cpu) {
+		c.machine.Put(cpu) // Already preempted.
+		return nil, usermem.NoAccess, platform.ErrContextInterrupt
+	}
+
+	// Mark the address space as dirty.
+	flags := ring0.Flags(0)
+	dirty := localAS.Touch(cpu)
+	if v := atomic.SwapUint32(dirty, 1); v == 0 {
+		flags |= ring0.FlagFlush
+	}
+	if ac.FullRestore() {
+		flags |= ring0.FlagFull
+	}
+
+	// Take the blue pill.
+	si, at, err := cpu.SwitchToUser(regs, fp, localAS.pageTables, flags)
+
+	// Release resources.
+	c.machine.Put(cpu)
+
+	// All done.
+	c.interrupt.Disable()
+	return si, at, err
+}
+
+// Interrupt interrupts the running context.
+func (c *context) Interrupt() {
+	c.interrupt.NotifyInterrupt()
+}