Re: [PATCH v5 14/22] virtio_pci: queue_reset: support VIRTIO_F_RING_RESET

[Jason Wang <jasowang@redhat.com>]

On Mon, Feb 14, 2022 at 4:14 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
>
> This patch implements virtio pci support for QUEUE RESET.
>
> Performing reset on a queue is divided into these steps:
>
> 1. reset_vq: reset one vq
> 2. recycle the buffer from vq by virtqueue_detach_unused_buf()
> 3. release the ring of the vq by vring_release_virtqueue()
> 4. enable_reset_vq: re-enable the reset queue
>
> This patch implements reset_vq, enable_reset_vq in the pci scenario.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> ---
>  drivers/virtio/virtio_pci_common.c |  8 ++--
>  drivers/virtio/virtio_pci_modern.c | 60 ++++++++++++++++++++++++++++++
>  2 files changed, 65 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> index 5a4f750a0b97..9ea319b1d404 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -255,9 +255,11 @@ static void vp_del_vq(struct virtqueue *vq)
>         struct virtio_pci_vq_info *info = vp_dev->vqs[vq->index];
>         unsigned long flags;
>
> -       spin_lock_irqsave(&vp_dev->lock, flags);
> -       list_del(&info->node);
> -       spin_unlock_irqrestore(&vp_dev->lock, flags);
> +       if (!vq->reset) {
> +               spin_lock_irqsave(&vp_dev->lock, flags);
> +               list_del(&info->node);
> +               spin_unlock_irqrestore(&vp_dev->lock, flags);
> +       }
>
>         vp_dev->del_vq(info);
>         kfree(info);
> diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> index bed3e9b84272..7d28f4c36fc2 100644
> --- a/drivers/virtio/virtio_pci_modern.c
> +++ b/drivers/virtio/virtio_pci_modern.c
> @@ -34,6 +34,9 @@ static void vp_transport_features(struct virtio_device *vdev, u64 features)
>         if ((features & BIT_ULL(VIRTIO_F_SR_IOV)) &&
>                         pci_find_ext_capability(pci_dev, PCI_EXT_CAP_ID_SRIOV))
>                 __virtio_set_bit(vdev, VIRTIO_F_SR_IOV);
> +
> +       if (features & BIT_ULL(VIRTIO_F_RING_RESET))
> +               __virtio_set_bit(vdev, VIRTIO_F_RING_RESET);
>  }
>
>  /* virtio config->finalize_features() implementation */
> @@ -176,6 +179,59 @@ static void vp_reset(struct virtio_device *vdev)
>         vp_disable_cbs(vdev);
>  }
>
> +static int vp_modern_reset_vq(struct virtqueue *vq)
> +{
> +       struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
> +       struct virtio_pci_modern_device *mdev = &vp_dev->mdev;
> +       struct virtio_pci_vq_info *info;
> +       unsigned long flags;
> +
> +       if (!virtio_has_feature(vq->vdev, VIRTIO_F_RING_RESET))
> +               return -ENOENT;
> +
> +       vp_modern_set_queue_reset(mdev, vq->index);
> +
> +       info = vp_dev->vqs[vq->index];
> +

Any reason that we don't need to disable irq here as the previous versions did?


> +       /* delete vq from irq handler */
> +       spin_lock_irqsave(&vp_dev->lock, flags);
> +       list_del(&info->node);
> +       spin_unlock_irqrestore(&vp_dev->lock, flags);
> +
> +       INIT_LIST_HEAD(&info->node);
> +
> +       vq->reset = VIRTQUEUE_RESET_STAGE_DEVICE;
> +
> +       return 0;
> +}
> +
> +static int vp_modern_enable_reset_vq(struct virtqueue *vq)
> +{
> +       struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
> +       struct virtio_pci_modern_device *mdev = &vp_dev->mdev;
> +       struct virtio_pci_vq_info *info;
> +       struct virtqueue *_vq;
> +
> +       if (vq->reset != VIRTQUEUE_RESET_STAGE_RELEASE)
> +               return -EBUSY;
> +
> +       /* check queue reset status */
> +       if (vp_modern_get_queue_reset(mdev, vq->index) != 1)
> +               return -EBUSY;
> +
> +       info = vp_dev->vqs[vq->index];
> +       _vq = vp_setup_vq(vq->vdev, vq->index, NULL, NULL, NULL,
> +                        info->msix_vector);

So we only care about moden devices, this means using vp_setup_vq()
with NULL seems tricky.

As replied in another thread, I would simply ask the caller to call
the vring reallocation helper. See the reply for patch 17.

Thanks


> +       if (IS_ERR(_vq)) {
> +               vq->reset = VIRTQUEUE_RESET_STAGE_RELEASE;
> +               return PTR_ERR(_vq);
> +       }
> +
> +       vp_modern_set_queue_enable(&vp_dev->mdev, vq->index, true);
> +
> +       return 0;
> +}
> +
>  static u16 vp_config_vector(struct virtio_pci_device *vp_dev, u16 vector)
>  {
>         return vp_modern_config_vector(&vp_dev->mdev, vector);
> @@ -397,6 +453,8 @@ static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
>         .set_vq_affinity = vp_set_vq_affinity,
>         .get_vq_affinity = vp_get_vq_affinity,
>         .get_shm_region  = vp_get_shm_region,
> +       .reset_vq        = vp_modern_reset_vq,
> +       .enable_reset_vq = vp_modern_enable_reset_vq,
>  };
>
>  static const struct virtio_config_ops virtio_pci_config_ops = {
> @@ -415,6 +473,8 @@ static const struct virtio_config_ops virtio_pci_config_ops = {
>         .set_vq_affinity = vp_set_vq_affinity,
>         .get_vq_affinity = vp_get_vq_affinity,
>         .get_shm_region  = vp_get_shm_region,
> +       .reset_vq        = vp_modern_reset_vq,
> +       .enable_reset_vq = vp_modern_enable_reset_vq,
>  };
>
>  /* the PCI probing function */
> --
> 2.31.0
>