Add vfioFD skeleton code for TPU v5e.

PiperOrigin-RevId: 585215723

pkg/sentry/devices/tpuproxy/BUILD

@@ -0,0 +1,18 @@
+load("//tools:defs.bzl", "go_library")
+
+package(default_applicable_licenses = ["//:license"])
+
+licenses(["notice"])
+
+go_library(
+    name = "tpuproxy",
+    srcs = ["tpu.go"],
+    deps = [
+        "//pkg/context",
+        "//pkg/errors/linuxerr",
+        "//pkg/sentry/arch",
+        "//pkg/sentry/vfs",
+        "//pkg/usermem",
+        "//pkg/waiter",
+    ],
+)

pkg/sentry/devices/tpuproxy/tpu.go

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+// Copyright 2023 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 tpuproxy implements proxying for TPU devices.
+package tpuproxy
+
+import (
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/usermem"
+	"gvisor.dev/gvisor/pkg/waiter"
+)
+
+// vfioFD implements vfs.FileDescriptionImpl for /dev/vfio/[0-9]+
+//
+// vfioFD is not savable until TPU save/restore is needed.
+type vfioFD struct {
+	vfsfd vfs.FileDescription
+	vfs.FileDescriptionDefaultImpl
+	vfs.DentryMetadataFileDescriptionImpl
+	vfs.NoLockFD
+}
+
+// Release implements vfs.FileDescriptionImpl.Release.
+func (fd *vfioFD) Release(context.Context) {
+}
+
+// EventRegister implements waiter.Waitable.EventRegister.
+func (fd *vfioFD) EventRegister(e *waiter.Entry) error {
+	return nil
+}
+
+// EventUnregister implements waiter.Waitable.EventUnregister.
+func (fd *vfioFD) EventUnregister(e *waiter.Entry) {
+}
+
+// Readiness implements waiter.Waitable.Readiness.
+func (fd *vfioFD) Readiness(mask waiter.EventMask) waiter.EventMask {
+	return waiter.EventErr
+}
+
+// Epollable implements vfs.FileDescriptionImpl.Epollable.
+func (fd *vfioFD) Epollable() bool {
+	return true
+}
+
+// Ioctl implements vfs.FileDescriptionImpl.Ioctl.
+func (fd *vfioFD) Ioctl(ctx context.Context, uio usermem.IO, sysno uintptr, args arch.SyscallArguments) (uintptr, error) {
+	return 0, linuxerr.ENOSYS
+}