Hi Stefan On Fri, May 22, 2020 at 7:18 PM Stefan Hajnoczi <stefa...@redhat.com> wrote: > > Many vhost devices in QEMU currently do not involve the device backend > in feature negotiation. This seems fine at first glance for device types > without their own feature bits (virtio-net has many but other device > types have none). > > This overlooks the fact that QEMU's virtqueue implementation and the > device backend's implementation may support different features. QEMU > must not report features to the guest that the the device backend > doesn't support. > > For example, QEMU supports VIRTIO 1.1 packed virtqueues while many > existing vhost device backends do not. When the user sets packed=on the > device backend breaks. This should have been handled gracefully by > feature negotiation instead. > > Introduce vhost_get_default_features() and update all vhost devices in > QEMU to involve the device backend in feature negotiation. > > This patch fixes the following error: > > $ x86_64-softmmu/qemu-system-x86_64 \ > -drive if=virtio,file=test.img,format=raw \ > -chardev socket,path=/tmp/vhost-user-blk.sock,id=char0 \ > -device vhost-user-blk-pci,chardev=char0,packed=on \ > -object memory-backend-memfd,size=1G,share=on,id=ram0 \ > -M accel=kvm,memory-backend=ram0 > qemu-system-x86_64: Failed to set msg fds. > qemu-system-x86_64: vhost VQ 0 ring restore failed: -1: Success (0) > > The vhost-user-blk backend failed as follows: > > $ ./vhost-user-blk --socket-path=/tmp/vhost-user-blk.sock -b test2.img > vu_panic: virtio: zero sized buffers are not allowed > virtio-blk request missing headers > > Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> > --- > include/hw/virtio/vhost.h | 1 + > include/hw/virtio/virtio-gpu.h | 2 ++ > include/sysemu/cryptodev-vhost.h | 11 +++++++++++ > backends/cryptodev-vhost.c | 19 +++++++++++++++++++ > hw/display/vhost-user-gpu.c | 17 +++++++++++++++++ > hw/display/virtio-gpu-base.c | 2 +- > hw/input/vhost-user-input.c | 9 +++++++++ > hw/virtio/vhost-user-fs.c | 5 +++-- > hw/virtio/vhost-vsock.c | 5 +++-- > hw/virtio/vhost.c | 22 ++++++++++++++++++++++ > hw/virtio/virtio-crypto.c | 3 ++- > 11 files changed, 90 insertions(+), 6 deletions(-) > > diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h > index 085450c6f8..d2e54dd4a8 100644 > --- a/include/hw/virtio/vhost.h > +++ b/include/hw/virtio/vhost.h > @@ -112,6 +112,7 @@ void vhost_virtqueue_mask(struct vhost_dev *hdev, > VirtIODevice *vdev, int n, > bool mask); > uint64_t vhost_get_features(struct vhost_dev *hdev, const int *feature_bits, > uint64_t features); > +uint64_t vhost_get_default_features(struct vhost_dev *hdev, uint64_t > features); > void vhost_ack_features(struct vhost_dev *hdev, const int *feature_bits, > uint64_t features); > bool vhost_has_free_slot(void); > diff --git a/include/hw/virtio/virtio-gpu.h b/include/hw/virtio/virtio-gpu.h > index 6dd57f2025..41d270d80e 100644 > --- a/include/hw/virtio/virtio-gpu.h > +++ b/include/hw/virtio/virtio-gpu.h > @@ -192,6 +192,8 @@ bool virtio_gpu_base_device_realize(DeviceState *qdev, > void virtio_gpu_base_reset(VirtIOGPUBase *g); > void virtio_gpu_base_fill_display_info(VirtIOGPUBase *g, > struct virtio_gpu_resp_display_info *dpy_info); > +uint64_t virtio_gpu_base_get_features(VirtIODevice *vdev, uint64_t features, > + Error **errp); > > /* virtio-gpu.c */ > void virtio_gpu_ctrl_response(VirtIOGPU *g, > diff --git a/include/sysemu/cryptodev-vhost.h > b/include/sysemu/cryptodev-vhost.h > index f42824fbde..e629446bfb 100644 > --- a/include/sysemu/cryptodev-vhost.h > +++ b/include/sysemu/cryptodev-vhost.h > @@ -122,6 +122,17 @@ int cryptodev_vhost_start(VirtIODevice *dev, int > total_queues); > */ > void cryptodev_vhost_stop(VirtIODevice *dev, int total_queues); > > +/** > + * cryptodev_vhost_get_features: > + * @dev: the virtio crypto object > + * @requested_features: the features being offered > + * > + * Returns: the requested features bits that are supported by the vhost > device, > + * or the original request feature bits if vhost is disabled > + * > + */ > +uint64_t cryptodev_vhost_get_features(VirtIODevice *dev, uint64_t features); > + > /** > * cryptodev_vhost_virtqueue_mask: > * @dev: the virtio crypto object > diff --git a/backends/cryptodev-vhost.c b/backends/cryptodev-vhost.c > index 8337c9a495..5f5a4fda7b 100644 > --- a/backends/cryptodev-vhost.c > +++ b/backends/cryptodev-vhost.c > @@ -266,6 +266,20 @@ void cryptodev_vhost_stop(VirtIODevice *dev, int > total_queues) > assert(r >= 0); > } > > +uint64_t cryptodev_vhost_get_features(VirtIODevice *dev, uint64_t features) > +{ > + VirtIOCrypto *vcrypto = VIRTIO_CRYPTO(dev); > + CryptoDevBackend *b = vcrypto->cryptodev; > + CryptoDevBackendClient *cc = b->conf.peers.ccs[0]; > + CryptoDevBackendVhost *vhost_crypto = cryptodev_get_vhost(cc, b, 0); > + > + if (!vhost_crypto) { > + return features; /* vhost disabled */ > + } > + > + return vhost_get_default_features(&vhost_crypto->dev, features); > +} > + > void cryptodev_vhost_virtqueue_mask(VirtIODevice *dev, > int queue, > int idx, bool mask) > @@ -333,6 +347,11 @@ void cryptodev_vhost_stop(VirtIODevice *dev, int > total_queues) > { > } > > +uint64_t cryptodev_vhost_get_features(VirtIODevice *dev, uint64_t features) > +{ > + return features; > +} > + > void cryptodev_vhost_virtqueue_mask(VirtIODevice *dev, > int queue, > int idx, bool mask) > diff --git a/hw/display/vhost-user-gpu.c b/hw/display/vhost-user-gpu.c > index 4cdaee1bde..e483df2a9e 100644 > --- a/hw/display/vhost-user-gpu.c > +++ b/hw/display/vhost-user-gpu.c > @@ -466,6 +466,22 @@ vhost_user_gpu_set_config(VirtIODevice *vdev, > } > } > > +static uint64_t > +vhost_user_gpu_get_features(VirtIODevice *vdev, uint64_t features, > + Error **errp) > +{ > + VhostUserGPU *g = VHOST_USER_GPU(vdev); > + Error *local_err = NULL; > + > + features = virtio_gpu_base_get_features(vdev, features, &local_err); > + if (local_err) { > + error_propagate(errp, local_err); > + return 0; > + } > + > + return vhost_get_default_features(&g->vhost->dev, features); > +} > + > static void > vhost_user_gpu_set_status(VirtIODevice *vdev, uint8_t val) > { > @@ -582,6 +598,7 @@ vhost_user_gpu_class_init(ObjectClass *klass, void *data) > > vdc->realize = vhost_user_gpu_device_realize; > vdc->reset = vhost_user_gpu_reset; > + vdc->get_features = vhost_user_gpu_get_features; > vdc->set_status = vhost_user_gpu_set_status; > vdc->guest_notifier_mask = vhost_user_gpu_guest_notifier_mask; > vdc->guest_notifier_pending = vhost_user_gpu_guest_notifier_pending; > diff --git a/hw/display/virtio-gpu-base.c b/hw/display/virtio-gpu-base.c > index c159351be3..05d1ff2db2 100644 > --- a/hw/display/virtio-gpu-base.c > +++ b/hw/display/virtio-gpu-base.c > @@ -176,7 +176,7 @@ virtio_gpu_base_device_realize(DeviceState *qdev, > return true; > } > > -static uint64_t > +uint64_t > virtio_gpu_base_get_features(VirtIODevice *vdev, uint64_t features, > Error **errp) > { > diff --git a/hw/input/vhost-user-input.c b/hw/input/vhost-user-input.c > index 63984a8ba7..1371fb32cc 100644 > --- a/hw/input/vhost-user-input.c > +++ b/hw/input/vhost-user-input.c > @@ -45,6 +45,14 @@ static void vhost_input_change_active(VirtIOInput *vinput) > } > } > > +static uint64_t vhost_input_get_features(VirtIODevice *vdev, uint64_t > features, > + Error **errp) > +{ > + VHostUserInput *vhi = VHOST_USER_INPUT(vdev); > + > + return vhost_get_default_features(&vhi->vhost->dev, features); > +} > + > static void vhost_input_get_config(VirtIODevice *vdev, uint8_t *config_data) > { > VirtIOInput *vinput = VIRTIO_INPUT(vdev); > @@ -89,6 +97,7 @@ static void vhost_input_class_init(ObjectClass *klass, void > *data) > DeviceClass *dc = DEVICE_CLASS(klass); > > dc->vmsd = &vmstate_vhost_input; > + vdc->get_features = vhost_input_get_features; > vdc->get_config = vhost_input_get_config; > vdc->set_config = vhost_input_set_config; > vic->realize = vhost_input_realize; > diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c > index 1bc5d03a00..56015ca3d4 100644 > --- a/hw/virtio/vhost-user-fs.c > +++ b/hw/virtio/vhost-user-fs.c > @@ -130,8 +130,9 @@ static uint64_t vuf_get_features(VirtIODevice *vdev, > uint64_t requested_features, > Error **errp) > { > - /* No feature bits used yet */ > - return requested_features; > + VHostUserFS *fs = VHOST_USER_FS(vdev); > + > + return vhost_get_default_features(&fs->vhost_dev, requested_features); > } > > static void vuf_handle_output(VirtIODevice *vdev, VirtQueue *vq) > diff --git a/hw/virtio/vhost-vsock.c b/hw/virtio/vhost-vsock.c > index 4a228f5168..7276587be6 100644 > --- a/hw/virtio/vhost-vsock.c > +++ b/hw/virtio/vhost-vsock.c > @@ -180,8 +180,9 @@ static uint64_t vhost_vsock_get_features(VirtIODevice > *vdev, > uint64_t requested_features, > Error **errp) > { > - /* No feature bits used yet */ > - return requested_features; > + VHostVSock *vsock = VHOST_VSOCK(vdev); > + > + return vhost_get_default_features(&vsock->vhost_dev, requested_features); > } > > static void vhost_vsock_handle_output(VirtIODevice *vdev, VirtQueue *vq) > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c > index aff98a0ede..f8a144dcd0 100644 > --- a/hw/virtio/vhost.c > +++ b/hw/virtio/vhost.c > @@ -48,6 +48,23 @@ static unsigned int used_memslots; > static QLIST_HEAD(, vhost_dev) vhost_devices = > QLIST_HEAD_INITIALIZER(vhost_devices); > > +/* > + * Feature bits that device backends must explicitly report. Feature bits not > + * listed here maybe set by QEMU without checking with the device backend. > + * Ideally all feature bits would be listed here but existing vhost device > + * implementations do not explicitly report bits like VIRTIO_F_VERSION_1, so > we > + * can only assume they are supported. > + * > + * New feature bits added to the VIRTIO spec should usually be included here > + * so that existing vhost device backends that do not support them yet > continue > + * to work. > + */ > +static const int vhost_default_feature_bits[] = { > + VIRTIO_F_IOMMU_PLATFORM, > + VIRTIO_F_RING_PACKED,
So effectively, we don't care about backend features except for those 2 bits, and an extra F_LOG_ALL check in vhost.c, right? It's not entirely clear to me how the feature flags of device and backend should combine tbh. > + VHOST_INVALID_FEATURE_BIT > +}; > + > bool vhost_has_free_slot(void) > { > unsigned int slots_limit = ~0U; > @@ -1468,6 +1485,11 @@ uint64_t vhost_get_features(struct vhost_dev *hdev, > const int *feature_bits, > return features; > } > > +uint64_t vhost_get_default_features(struct vhost_dev *hdev, uint64_t > features) > +{ > + return vhost_get_features(hdev, vhost_default_feature_bits, features); > +} > + > void vhost_ack_features(struct vhost_dev *hdev, const int *feature_bits, > uint64_t features) > { > diff --git a/hw/virtio/virtio-crypto.c b/hw/virtio/virtio-crypto.c > index bd9165c565..ef711b56f4 100644 > --- a/hw/virtio/virtio-crypto.c > +++ b/hw/virtio/virtio-crypto.c > @@ -739,7 +739,8 @@ static uint64_t virtio_crypto_get_features(VirtIODevice > *vdev, > uint64_t features, > Error **errp) > { > - return features; > + /* Just returns features when vhost is disabled */ > + return cryptodev_vhost_get_features(vdev, features); > } > > static void virtio_crypto_reset(VirtIODevice *vdev) > -- > 2.25.3 >