Add an initial implementation for vfioDevice Open, which implements vfs.Device interface.

PiperOrigin-RevId: 586047954

pkg/sentry/devices/tpuproxy/BUILD

@@ -6,13 +6,20 @@ licenses(["notice"])
 
 go_library(
     name = "tpuproxy",
-    srcs = ["tpu.go"],
+    srcs = [
+        "device.go",
+        "tpu.go",
+    ],
     deps = [
         "//pkg/context",
+        "//pkg/devutil",
         "//pkg/errors/linuxerr",
+        "//pkg/log",
         "//pkg/sentry/arch",
         "//pkg/sentry/vfs",
+        "//pkg/sync",
         "//pkg/usermem",
         "//pkg/waiter",
+        "@org_golang_x_sys//unix:go_default_library",
     ],
 )

pkg/sentry/devices/tpuproxy/device.go

@@ -0,0 +1,64 @@
+// 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
+
+import (
+	"fmt"
+
+	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/devutil"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
+	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sync"
+)
+
+// vfioDevice implements vfs.Device for /dev/vfio/[0-9]+
+//
+// +stateify savable
+type vfioDevice struct {
+	mu sync.Mutex
+
+	minor uint32
+}
+
+// Open implememnts vfs.Device.Open.
+func (dev *vfioDevice) Open(ctx context.Context, mnt *vfs.Mount, d *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
+	devClient := devutil.GoferClientFromContext(ctx)
+	if devClient == nil {
+		log.Warningf("devutil.CtxDevGoferClient is not set")
+		return nil, linuxerr.ENOENT
+	}
+	dev.mu.Lock()
+	defer dev.mu.Unlock()
+	devName := fmt.Sprintf("/dev/vfio/%d", dev.minor)
+	hostFD, err := devClient.OpenAt(ctx, devName, opts.Flags)
+	if err != nil {
+		ctx.Warningf("vfioDevice: failed to open host %s: %v", devName, err)
+		return nil, err
+	}
+	fd := &vfioFD{
+		hostFD: int32(hostFD),
+		device: dev,
+	}
+	if err := fd.vfsfd.Init(fd, opts.Flags, mnt, d, &vfs.FileDescriptionOptions{
+		UseDentryMetadata: true,
+	}); err != nil {
+		unix.Close(hostFD)
+		return nil, err
+	}
+	return &fd.vfsfd, nil
+}

pkg/sentry/devices/tpuproxy/tpu.go

@@ -32,6 +32,9 @@ type vfioFD struct {
 	vfs.FileDescriptionDefaultImpl
 	vfs.DentryMetadataFileDescriptionImpl
 	vfs.NoLockFD
+
+	hostFD int32
+	device *vfioDevice
 }
 
 // Release implements vfs.FileDescriptionImpl.Release.