Re: [PATCH v9 23/32] virtio_pci: queue_reset: support VIRTIO_F_RING_RESET

[Jason Wang <jasowang@redhat.com>]

在 2022/4/6 上午11:43, Xuan Zhuo 写道:
> This patch implements virtio pci support for QUEUE RESET.
>
> Performing reset on a queue is divided into these steps:
>
>   1. notify the device to reset the queue
>   2. recycle the buffer submitted
>   3. reset the vring (may re-alloc)
>   4. mmap vring to device, and enable the queue
>
> This patch implements virtio_reset_vq(), virtio_enable_resetq() 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 | 84 ++++++++++++++++++++++++++++++
>   drivers/virtio/virtio_ring.c       |  2 +
>   include/linux/virtio.h             |  1 +
>   4 files changed, 92 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> index fdbde1db5ec5..863d3a8a0956 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -248,9 +248,11 @@ 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) {


On which condition that we may hit this path?


> +		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 49a4493732cf..cb5d38f1c9c8 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 */
> @@ -199,6 +202,83 @@ static int vp_active_vq(struct virtqueue *vq, u16 msix_vec)
>   	return 0;
>   }
>   
> +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];
> +
> +	/* 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);
> +
> +	/* For the case where vq has an exclusive irq, to prevent the irq from
> +	 * being received again and the pending irq, call disable_irq().
> +	 *
> +	 * In the scenario based on shared interrupts, vq will be searched from
> +	 * the queue virtqueues. Since the previous list_del() has been deleted
> +	 * from the queue, it is impossible for vq to be called in this case.
> +	 * There is no need to close the corresponding interrupt.
> +	 */
> +	if (vp_dev->per_vq_vectors && info->msix_vector != VIRTIO_MSI_NO_VECTOR)
> +		disable_irq(pci_irq_vector(vp_dev->pci_dev, info->msix_vector));


See the previous discussion and the revert of the first try to harden 
the interrupt. We probably can't use disable_irq() since it conflicts 
with the affinity managed IRQ that is used by some drivers.

We need to use synchonize_irq() and per virtqueue flag instead. As 
mentioned in previous patches, this could be done on top of my rework on 
the IRQ hardening .


> +
> +	vq->reset = true;
> +
> +	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;
> +	unsigned long flags, index;
> +	int err;
> +
> +	if (!vq->reset)
> +		return -EBUSY;
> +
> +	index = vq->index;
> +	info = vp_dev->vqs[index];
> +
> +	/* check queue reset status */
> +	if (vp_modern_get_queue_reset(mdev, index) != 1)
> +		return -EBUSY;
> +
> +	err = vp_active_vq(vq, info->msix_vector);
> +	if (err)
> +		return err;
> +
> +	if (vq->callback) {
> +		spin_lock_irqsave(&vp_dev->lock, flags);
> +		list_add(&info->node, &vp_dev->virtqueues);
> +		spin_unlock_irqrestore(&vp_dev->lock, flags);
> +	} else {
> +		INIT_LIST_HEAD(&info->node);
> +	}
> +
> +	vp_modern_set_queue_enable(&vp_dev->mdev, index, true);
> +
> +	if (vp_dev->per_vq_vectors && info->msix_vector != VIRTIO_MSI_NO_VECTOR)
> +		enable_irq(pci_irq_vector(vp_dev->pci_dev, info->msix_vector));


We had the same issue as disable_irq().

Thanks


> +
> +	vq->reset = false;
> +
> +	return 0;
> +}
> +
>   static u16 vp_config_vector(struct virtio_pci_device *vp_dev, u16 vector)
>   {
>   	return vp_modern_config_vector(&vp_dev->mdev, vector);
> @@ -407,6 +487,8 @@ 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 = {
> @@ -425,6 +507,8 @@ 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 */
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 6250e19fc5bf..91937e21edca 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -2028,6 +2028,7 @@ static struct virtqueue *vring_create_virtqueue_packed(
>   	vq->vq.vdev = vdev;
>   	vq->vq.name = name;
>   	vq->vq.index = index;
> +	vq->vq.reset = false;
>   	vq->notify = notify;
>   	vq->weak_barriers = weak_barriers;
>   
> @@ -2508,6 +2509,7 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
>   	vq->vq.vdev = vdev;
>   	vq->vq.name = name;
>   	vq->vq.index = index;
> +	vq->vq.reset = false;
>   	vq->notify = notify;
>   	vq->weak_barriers = weak_barriers;
>   
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index c86ff02e0ca0..33ab003c5100 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -33,6 +33,7 @@ struct virtqueue {
>   	unsigned int num_free;
>   	unsigned int num_max;
>   	void *priv;
> +	bool reset;
>   };
>   
>   int virtqueue_add_outbuf(struct virtqueue *vq,