From: Jason Wang <jasowang@redhat.com>
To: Stefan Hajnoczi <stefanha@redhat.com>, qemu-devel@nongnu.org
Cc: "Kevin Wolf" <kwolf@redhat.com>,
"Laurent Vivier" <lvivier@redhat.com>,
"Thomas Huth" <thuth@redhat.com>,
"Eduardo Habkost" <ehabkost@redhat.com>,
qemu-block@nongnu.org, "Michael S. Tsirkin" <mst@redhat.com>,
cohuck@redhat.com, "Dr. David Alan Gilbert" <dgilbert@redhat.com>,
"Raphael Norwitz" <raphael.norwitz@nutanix.com>,
"Gonglei (Arei)" <arei.gonglei@huawei.com>,
"Gerd Hoffmann" <kraxel@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Marc-André Lureau" <marcandre.lureau@redhat.com>,
"Fam Zheng" <fam@euphon.net>, "Max Reitz" <mreitz@redhat.com>
Subject: Re: [PATCH 2/5] vhost: involve device backends in feature negotiation
Date: Fri, 29 May 2020 15:04:54 +0800 [thread overview]
Message-ID: <c99670df-8f73-2a13-1e41-0d0a3aac0133@redhat.com> (raw)
In-Reply-To: <20200522171726.648279-3-stefanha@redhat.com>
On 2020/5/23 上午1:17, Stefan Hajnoczi 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)
It looks to me this could be fixed simply by adding VIRTIO_F_RING_PACKED
into user_feature_bits in vhost-user-blk.c.
And for the rest, we need require them to call vhost_get_features() with
the proper feature bits that needs to be acked by the backend.
>
> 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 <stefanha@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.
For most backends, we care about the features for datapath. So this is
not true at least for networking device, since VIRTIO_F_VERSION_1 have
impact on the length of vnet header length.
> + *
> + * 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.
It actually depends on the type of backend.
Kernel vhost-net does not validate GSO features since qemu can talk
directly to TAP and vhost doesn't report those features. But for
vhost-user GSO features must be validated by qemu since qemu can't see
what is behind vhost-user.
> + */
> +static const int vhost_default_feature_bits[] = {
> + VIRTIO_F_IOMMU_PLATFORM,
> + VIRTIO_F_RING_PACKED,
> + 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);
> +}
There's probably no need for a new helper, we can do all these inside
vhost_get_features().
Thanks
> +
> 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)
next prev parent reply other threads:[~2020-05-29 7:09 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-22 17:17 [PATCH 0/5] virtio: enable VIRTIO_F_RING_PACKED for all devices Stefan Hajnoczi
2020-05-22 17:17 ` [PATCH 1/5] tests/libqos: mask out VIRTIO_F_RING_PACKED for now Stefan Hajnoczi
2020-05-22 19:21 ` Thomas Huth
2020-05-22 17:17 ` [PATCH 2/5] vhost: involve device backends in feature negotiation Stefan Hajnoczi
2020-05-27 14:28 ` Marc-André Lureau
2020-05-29 15:20 ` Stefan Hajnoczi
2020-05-29 7:04 ` Jason Wang [this message]
2020-05-29 13:56 ` Stefan Hajnoczi
2020-05-29 14:29 ` Dr. David Alan Gilbert
2020-06-03 14:44 ` Stefan Hajnoczi
2020-06-01 12:51 ` Jason Wang
2020-06-03 14:39 ` Stefan Hajnoczi
2020-05-22 17:17 ` [PATCH 3/5] vhost-user-blk: add VIRTIO_F_RING_PACKED feature bit Stefan Hajnoczi
2020-05-25 4:06 ` Raphael Norwitz
2020-05-22 17:17 ` [PATCH 4/5] vhost-scsi: add VIRTIO_F_VERSION_1 and VIRTIO_F_RING_PACKED Stefan Hajnoczi
2020-05-25 4:02 ` Raphael Norwitz
2020-05-22 17:17 ` [PATCH 5/5] virtio: enable VIRTIO_F_RING_PACKED for all devices Stefan Hajnoczi
2020-05-26 17:29 ` Dr. David Alan Gilbert
2020-05-29 7:15 ` Jason Wang
2020-05-29 15:28 ` Stefan Hajnoczi
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