Make gVisor search for all potential registered TPU devices.

gVisor creates symlinks under /sys/class when the device presents.

PiperOrigin-RevId: 588222909

pkg/sentry/fsimpl/sys/pci.go

@@ -15,6 +15,7 @@
 package sys
 
 import (
+	"errors"
 	"fmt"
 	"path"
 	regex "regexp"
@@ -27,7 +28,11 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 )
 
-const pciMainBusDevicePath = "/sys/devices/pci0000:00"
+const (
+	pciMainBusDevicePath = "/sys/devices/pci0000:00"
+	accelDevice          = "accel"
+	vfioDevice           = "vfio-dev"
+)
 
 var (
 	// Matches PCI device addresses in the main domain.
@@ -48,25 +53,37 @@ var (
 	}
 )
 
-// Create /sys/class/accel/accel# symlinks.
-func (fs *filesystem) newAccelDir(ctx context.Context, creds *auth.Credentials) (map[string]kernfs.Inode, error) {
-	accelDirs := map[string]kernfs.Inode{}
+// Creates TPU devices' symlinks under /sys/class/. TPU deivce type that are not present on host willl be ignored.
+// TPU v4 symlinks are created at /sys/class/accel/accel#.
+// TPU v5 symlinks go to /sys/class/vfio-dev/vfio#.
+func (fs *filesystem) newDeviceClassDir(ctx context.Context, creds *auth.Credentials, tpuDeviceTypes []string) (map[string]map[string]kernfs.Inode, error) {
+	dirs := map[string]map[string]kernfs.Inode{}
 	pciDents, err := hostDirEntries(pciMainBusDevicePath)
 	if err != nil {
 		return nil, err
 	}
 	for _, pciDent := range pciDents {
-		accelDents, err := hostDirEntries(path.Join(pciMainBusDevicePath, pciDent, "accel"))
-		if err != nil {
-			return nil, err
-		}
-		if len(accelDents) != 1 {
-			return nil, fmt.Errorf("path %q should only have one entry", path.Join(pciMainBusDevicePath, pciDent, "accel"))
+		for _, tpuDeviceType := range tpuDeviceTypes {
+			subPath := path.Join(pciMainBusDevicePath, pciDent, tpuDeviceType)
+			dirs[tpuDeviceType] = map[string]kernfs.Inode{}
+			deviceDents, err := hostDirEntries(subPath)
+			if err != nil {
+				// Skips the path that doesn't exist.
+				if err == unix.ENOENT {
+					continue
+				}
+				return nil, err
+			}
+			if numOfDeviceDents := len(deviceDents); numOfDeviceDents != 1 {
+				return nil, fmt.Errorf("exactly one entry is expected at %v while there are %d", subPath, numOfDeviceDents)
+			}
+			dirs[tpuDeviceType][deviceDents[0]] = kernfs.NewStaticSymlink(ctx, creds, linux.UNNAMED_MAJOR, fs.devMinor, fs.NextIno(), fmt.Sprintf("../../devices/pci0000:00/%s/%s/%s", pciDent, tpuDeviceType, deviceDents[0]))
 		}
-		accelDirs[accelDents[0]] = kernfs.NewStaticSymlink(ctx, creds, linux.UNNAMED_MAJOR, fs.devMinor, fs.NextIno(), fmt.Sprintf("../../devices/pci0000:00/%s/accel/%s", pciDent, accelDents[0]))
 	}
-
-	return accelDirs, nil
+	if len(dirs) == 0 {
+		return nil, errors.New("no TPU device sysfile is found")
+	}
+	return dirs, nil
 }
 
 // Create /sys/bus/pci/devices symlinks.

pkg/sentry/fsimpl/sys/sys.go

@@ -53,9 +53,9 @@ type FilesystemType struct{}
 type InternalData struct {
 	// ProductName is the value to be set to devices/virtual/dmi/id/product_name.
 	ProductName string
-	// EnableAccelSysfs is whether to populate sysfs paths used by hardware
+	// EnableTPUProxyPaths is whether to populate sysfs paths used by hardware
 	// accelerators.
-	EnableAccelSysfs bool
+	EnableTPUProxyPaths bool
 }
 
 // filesystem implements vfs.FilesystemImpl.
@@ -126,19 +126,21 @@ func (fsType FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.Virt
 	if opts.InternalData != nil {
 		idata := opts.InternalData.(*InternalData)
 		productName = idata.ProductName
-		if idata.EnableAccelSysfs {
+		if idata.EnableTPUProxyPaths {
 			pciMainBusSub, err := fs.mirrorPCIBusDeviceDir(ctx, creds, pciMainBusDevicePath)
 			if err != nil {
 				return nil, nil, err
 			}
 			devicesSub["pci0000:00"] = fs.newDir(ctx, creds, defaultSysDirMode, pciMainBusSub)
 
-			accelSub, err := fs.newAccelDir(ctx, creds)
+			deviceDirs, err := fs.newDeviceClassDir(ctx, creds, []string{accelDevice, vfioDevice})
 			if err != nil {
 				return nil, nil, err
 			}
-			classSub["accel"] = fs.newDir(ctx, creds, defaultSysDirMode, accelSub)
 
+			for tpuDeviceType, symlinkDir := range deviceDirs {
+				classSub[tpuDeviceType] = fs.newDir(ctx, creds, defaultSysDirMode, symlinkDir)
+			}
 			pciDevicesSub, err := fs.newPCIDevicesDir(ctx, creds)
 			if err != nil {
 				return nil, nil, err

runsc/boot/vfs.go

@@ -857,7 +857,7 @@ func getMountNameAndOptions(spec *specs.Spec, conf *config.Config, m *mountInfo,
 		fsName = sys.Name
 
 	case sys.Name:
-		sysData := &sys.InternalData{EnableAccelSysfs: specutils.TPUProxyIsEnabled(spec, conf)}
+		sysData := &sys.InternalData{EnableTPUProxyPaths: specutils.TPUProxyIsEnabled(spec, conf)}
 		if len(productName) > 0 {
 			sysData.ProductName = productName
 		}