nvproxy: Add option to use the device gofer optionally.

We always use the device gofer in runsc, because the sandbox's filesystem
does not have the GPU devices mounted in it.

PiperOrigin-RevId: 736316547

Author: ayushr2

pkg/sentry/devices/nvproxy/frontend.go

@@ -16,6 +16,7 @@ package nvproxy
 
 import (
 	"fmt"
+	"path/filepath"
 
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -55,32 +56,43 @@ func (dev *frontendDevice) basename() string {
 
 // Open implements vfs.Device.Open.
 func (dev *frontendDevice) Open(ctx context.Context, mnt *vfs.Mount, vfsd *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
+	fd := &frontendFD{
+		dev: dev,
 	}
 	basename := dev.basename()
-	hostFD, err := devClient.OpenAt(ctx, basename, opts.Flags)
-	if err != nil {
-		ctx.Warningf("nvproxy: failed to open host %s: %v", basename, err)
-		return nil, err
-	}
-	fd := &frontendFD{
-		dev:           dev,
-		containerName: devClient.ContainerName(),
-		hostFD:        int32(hostFD),
+	if dev.nvp.useDevGofer {
+		devClient := devutil.GoferClientFromContext(ctx)
+		if devClient == nil {
+			log.Warningf("devutil.CtxDevGoferClient is not set")
+			return nil, linuxerr.ENOENT
+		}
+		fd.containerName = devClient.ContainerName()
+		hostFD, err := devClient.OpenAt(ctx, basename, opts.Flags)
+		if err != nil {
+			ctx.Warningf("nvproxy: failed to open %s: %v", basename, err)
+			return nil, err
+		}
+		fd.hostFD = int32(hostFD)
+	} else {
+		devPath := filepath.Join("/dev", basename)
+		flags := int(opts.Flags&unix.O_ACCMODE | unix.O_NOFOLLOW)
+		hostFD, err := unix.Openat(-1, devPath, flags, 0)
+		if err != nil {
+			ctx.Warningf("nvproxy: failed to open host %s: %v", devPath, err)
+			return nil, err
+		}
+		fd.hostFD = int32(hostFD)
 	}
 	if err := fd.vfsfd.Init(fd, opts.Flags, mnt, vfsd, &vfs.FileDescriptionOptions{
 		UseDentryMetadata: true,
 	}); err != nil {
-		unix.Close(hostFD)
+		unix.Close(int(fd.hostFD))
 		return nil, err
 	}
 	fd.internalEntry.Init(fd, waiter.AllEvents)
 	fd.internalQueue.EventRegister(&fd.internalEntry)
-	if err := fdnotifier.AddFD(int32(hostFD), &fd.internalQueue); err != nil {
-		unix.Close(hostFD)
+	if err := fdnotifier.AddFD(fd.hostFD, &fd.internalQueue); err != nil {
+		unix.Close(int(fd.hostFD))
 		return nil, err
 	}
 	fd.memmapFile.fd = fd

pkg/sentry/devices/nvproxy/nvproxy.go

@@ -30,7 +30,7 @@ import (
 )
 
 // Register registers all devices implemented by this package in vfsObj.
-func Register(vfsObj *vfs.VirtualFilesystem, version nvconf.DriverVersion, driverCaps nvconf.DriverCaps, uvmDevMajor uint32) error {
+func Register(vfsObj *vfs.VirtualFilesystem, version nvconf.DriverVersion, driverCaps nvconf.DriverCaps, uvmDevMajor uint32, useDevGofer bool) error {
 	// The kernel driver's interface is unstable, so only allow versions of the
 	// driver that are known to be supported.
 	log.Infof("NVIDIA driver version: %s", version)
@@ -45,6 +45,7 @@ func Register(vfsObj *vfs.VirtualFilesystem, version nvconf.DriverVersion, drive
 		abi:         abiCons.cons(),
 		version:     version,
 		capsEnabled: driverCaps,
+		useDevGofer: useDevGofer,
 		frontendFDs: make(map[*frontendFD]struct{}),
 		clients:     make(map[nvgpu.Handle]*rootClient),
 		objsFreeSet: make(map[*object]struct{}),
@@ -74,6 +75,7 @@ type nvproxy struct {
 	abi         *driverABI `state:"nosave"`
 	version     nvconf.DriverVersion
 	capsEnabled nvconf.DriverCaps
+	useDevGofer bool
 
 	fdsMu       fdsMutex `state:"nosave"`
 	frontendFDs map[*frontendFD]struct{}

pkg/sentry/devices/nvproxy/uvm.go

@@ -41,29 +41,39 @@ type uvmDevice struct {
 
 // Open implements vfs.Device.Open.
 func (dev *uvmDevice) Open(ctx context.Context, mnt *vfs.Mount, vfsd *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
-	}
-	hostFD, err := devClient.OpenAt(ctx, "nvidia-uvm", opts.Flags)
-	if err != nil {
-		ctx.Warningf("nvproxy: failed to open host /dev/nvidia-uvm: %v", err)
-		return nil, err
-	}
 	fd := &uvmFD{
-		dev:           dev,
-		containerName: devClient.ContainerName(),
-		hostFD:        int32(hostFD),
+		dev: dev,
+	}
+	if dev.nvp.useDevGofer {
+		devClient := devutil.GoferClientFromContext(ctx)
+		if devClient == nil {
+			log.Warningf("devutil.CtxDevGoferClient is not set")
+			return nil, linuxerr.ENOENT
+		}
+		fd.containerName = devClient.ContainerName()
+		hostFD, err := devClient.OpenAt(ctx, "nvidia-uvm", opts.Flags)
+		if err != nil {
+			ctx.Warningf("nvproxy: failed to open nvidia-uvm: %v", err)
+			return nil, err
+		}
+		fd.hostFD = int32(hostFD)
+	} else {
+		flags := int(opts.Flags&unix.O_ACCMODE | unix.O_NOFOLLOW)
+		hostFD, err := unix.Openat(-1, "/dev/nvidia-uvm", flags, 0)
+		if err != nil {
+			ctx.Warningf("nvproxy: failed to open host /dev/nvidia-uvm: %v", err)
+			return nil, err
+		}
+		fd.hostFD = int32(hostFD)
 	}
 	if err := fd.vfsfd.Init(fd, opts.Flags, mnt, vfsd, &vfs.FileDescriptionOptions{
 		UseDentryMetadata: true,
 	}); err != nil {
-		unix.Close(hostFD)
+		unix.Close(int(fd.hostFD))
 		return nil, err
 	}
-	if err := fdnotifier.AddFD(int32(hostFD), &fd.queue); err != nil {
-		unix.Close(hostFD)
+	if err := fdnotifier.AddFD(fd.hostFD, &fd.queue); err != nil {
+		unix.Close(int(fd.hostFD))
 		return nil, err
 	}
 	fd.memmapFile.fd = fd

runsc/boot/vfs.go

@@ -1401,7 +1401,7 @@ func nvproxyRegisterDevices(info *containerInfo, vfsObj *vfs.VirtualFilesystem)
 	if err != nil {
 		return fmt.Errorf("reserving device major number for nvidia-uvm: %w", err)
 	}
-	if err := nvproxy.Register(vfsObj, info.nvidiaDriverVersion, driverCaps, uvmDevMajor); err != nil {
+	if err := nvproxy.Register(vfsObj, info.nvidiaDriverVersion, driverCaps, uvmDevMajor, true /* useDevGofer */); err != nil {
 		return fmt.Errorf("registering nvproxy driver: %w", err)
 	}
 	info.nvidiaUVMDevMajor = uvmDevMajor