Re: [PATCH v4 14/14] virtio_pci: queue_reset: support VIRTIO_F_RING_RESET

On Fri, Feb 11, 2022 at 3:24 PM Xuan Zhuo [off-list ref] wrote:

On Fri, 11 Feb 2022 15:05:40 +0800, Jason Wang [off-list ref] wrote:

quoted

在 2022/2/9 下午8:29, Xuan Zhuo 写道:

quoted

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 | 80 ++++++++++++++++++++++++++++--
  drivers/virtio/virtio_ring.c       |  2 +
  include/linux/virtio.h             |  1 +
  4 files changed, 85 insertions(+), 6 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index cb01eb0cb2e4..303637ac4914 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 d29d40bf0b45..cc45515eda50 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 +179,70 @@ 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;
+   u16 msix_vec;
+
+   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];
+   msix_vec = info->msix_vector;
+
+   /* Disable VQ callback. */
+   if (vp_dev->per_vq_vectors && msix_vec != VIRTIO_MSI_NO_VECTOR)
+           disable_irq(pci_irq_vector(vp_dev->pci_dev, msix_vec));

I think we need a comment to explain why per_vq_mode needs to be dealt
with differently.

OK.

quoted

quoted

+
+   /* delete vq */
+   spin_lock_irqsave(&vp_dev->lock, flags);
+   list_del(&info->node);
+   spin_unlock_irqrestore(&vp_dev->lock, flags);

So I don't see where vring is freed and vp_setup_vq() may try to
allocate new memory, won't it be a memory leak in this case?

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

vring_release_virtqueue() (#8 patch) will release the vring.
That is called by the driver.

I think I should add a check to vp_modern_enable_reset_vq() that
vring_release_virtqueue() has already been called.

I wonder if we can have a better API.

Consider we know there's a requirement of vring re-allocation. I
wonder how about adding per vq config ops like:

del_vq()
find_vq()

We can limit them only after a virtqueue is reset before it is
enabled. We can have a full allocation on the resources e.g interrupt
(if some codes could be reused).

Then a driver can do
reset_vq()
detach_unused_buf()
del_vq
find_vq() /* with new parameters like ring_num and others like find_vqs() */
enable_reset_vq()

?

Thanks

Thanks

quoted

Thanks

quoted

+
+   vq->reset = true;
+
+   INIT_LIST_HEAD(&info->node);
+
+   return 0;
+}
+
+static int vp_modern_enable_reset_vq(struct virtqueue *vq, u16 ring_num)
+{
+   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;
+   u16 msix_vec;
+
+   if (!vq->reset)
+           return -EPERM;
+
+   /* 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, ring_num);
+   if (IS_ERR(_vq)) {
+           vq->reset = true;
+           return PTR_ERR(_vq);
+   }
+
+   vp_modern_set_queue_enable(&vp_dev->mdev, vq->index, true);
+
+   msix_vec = vp_dev->vqs[vq->index]->msix_vector;
+   if (vp_dev->per_vq_vectors && msix_vec != VIRTIO_MSI_NO_VECTOR)
+           enable_irq(pci_irq_vector(vp_dev->pci_dev, msix_vec));
+
+   return 0;
+}
+
  static u16 vp_config_vector(struct virtio_pci_device *vp_dev, u16 vector)
  {
    return vp_modern_config_vector(&vp_dev->mdev, vector);

@@ -231,10 +298,13 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
                            virtqueue_get_avail_addr(vq),
                            virtqueue_get_used_addr(vq));

-   vq->priv = (void __force *)vp_modern_map_vq_notify(mdev, index, NULL);
    if (!vq->priv) {
-           err = -ENOMEM;
-           goto err_map_notify;
+           vq->priv = (void __force *)vp_modern_map_vq_notify(mdev, index,
+                                                              NULL);
+           if (!vq->priv) {
+                   err = -ENOMEM;
+                   goto err_map_notify;
+           }

This seems unrelated or an artifact of previous patches?

Thanks

quoted

    }

    if (msix_vec != VIRTIO_MSI_NO_VECTOR) {

@@ -402,6 +472,8 @@ 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 = {

@@ -420,6 +492,8 @@ 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 b8747df8dc1f..4f6028e1e2d9 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c

@@ -1731,6 +1731,7 @@ static struct virtqueue *vring_create_virtqueue_packed(
    vq->vq.vdev = vdev;
    vq->vq.num_free = num;
    vq->vq.index = index;
+   vq->vq.reset = false;
    vq->we_own_ring = true;
    vq->notify = notify;
    vq->weak_barriers = weak_barriers;

@@ -2220,6 +2221,7 @@ static int __vring_init_virtqueue(struct virtqueue *_vq,
    vq->vq.vdev = vdev;
    vq->vq.num_free = vring.num;
    vq->vq.index = index;
+   vq->vq.reset = false;
    vq->we_own_ring = false;
    vq->notify = notify;
    vq->weak_barriers = weak_barriers;

diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index dd1657c3a488..5d4817d79f3f 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h

@@ -32,6 +32,7 @@ struct virtqueue {
    unsigned int index;
    unsigned int num_free;
    void *priv;
+   bool reset;
  };

  int virtqueue_add_outbuf(struct virtqueue *vq,

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