Re: [PATCH v7 17/26] virtio_pci: queue_reset: support VIRTIO_F_RING_RESET

Jason Wang
2022-03-09T08:54:31Z

在 2022/3/8 下午8:35, Xuan Zhuo 写道:
> This patch implements virtio pci support for QUEUE RESET.
>
> Performing reset on a queue is divided into these steps:
>
> 1. virtio_reset_vq() - notify the device to reset the queue
> 2. virtqueue_detach_unused_buf() - recycle the buffer submitted
> 3. virtqueue_reset_vring() - reset the vring (may re-alloc)
> 4. virtio_enable_resetq() - 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 | 83 ++++++++++++++++++++++++++++++
> 2 files changed, 88 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) {
> + 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..3c67d3607802 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 +202,82 @@ 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;
> + unsigned int irq;
> +
> + 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);
> +
> + vq->reset = VIRTIO_VQ_RESET_STEP_DEVICE;
> +
> + /* sync irq callback. */
> + if (vp_dev->intx_enabled) {
> + irq = vp_dev->pci_dev->irq;
> +
> + } else {
> + if (info->msix_vector == VIRTIO_MSI_NO_VECTOR)
> + return 0;
> +
> + irq = pci_irq_vector(vp_dev->pci_dev, info->msix_vector);
> + }
> +
> + synchronize_irq(irq);

Synchronize_irq() is not sufficient here since it breaks the effort of
the interrupt hardening which is done by commits:

080cd7c3ac87 virtio-pci: harden INTX interrupts
9e35276a5344 virtio_pci: harden MSI-X interrupts

Unfortunately  080cd7c3ac87 introduces an issue that disable_irq() were
used for the affinity managed irq but we're discussing a fix.

> +
> + 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 != VIRTIO_VQ_RESET_STEP_VRING_ATTACH)
> + 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);

Any reason we need to check queue_enable() here?

Thanks

> + vq->reset = VIRTIO_VQ_RESET_STEP_NONE;
> +
> + 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 +486,8 @@ 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 +506,8 @@ 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 */