On Wed, Jul 10, 2024 at 08:36:00AM +0200, Jiri Pirko wrote:
> From: Jiri Pirko <jiri@xxxxxxxxxx>
>
> Currently, the code waits in a busy loop on every admin virtqueue issued
> command to get a reply. That prevents callers from issuing multiple
> commands in parallel.
>
> To overcome this limitation, introduce a virtqueue event callback for
> admin virtqueue. For every issued command, use completion mechanism
> to wait on a reply. In the event callback, trigger the completion
> is done for every incoming reply.
>
> Alongside with that, introduce a spin lock to protect the admin
> virtqueue operations.
>
> Signed-off-by: Jiri Pirko <jiri@xxxxxxxxxx>
> ---
> v1->v2:
> - rebased on top of newly added patches
> - rebased on top of changes in previous patches (vq info, vqs[])
> - removed WARN_ON_ONCE() when calling virtqueue_kick()
> - added virtqueue_is_broken check in virtqueue_exec_admin_cmd() loop
> - added vp_modern_avq_cleanup() implementation to handle surprise
> removal case
> ---
> drivers/virtio/virtio_pci_common.c | 13 ++++--
> drivers/virtio/virtio_pci_common.h | 3 ++
> drivers/virtio/virtio_pci_modern.c | 74 +++++++++++++++++++++++++-----
> include/linux/virtio.h | 3 ++
> 4 files changed, 77 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> index 267643bb1cd5..c44d8ba00c02 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -395,6 +395,8 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned int nvqs,
> if (vqi->name && vqi->callback)
> ++nvectors;
> }
> + if (avq_num && vector_policy == VP_VQ_VECTOR_POLICY_EACH)
> + ++nvectors;
> } else {
> /* Second best: one for change, shared for all vqs. */
> nvectors = 2;
> @@ -425,9 +427,9 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned int nvqs,
> if (!avq_num)
> return 0;
> sprintf(avq->name, "avq.%u", avq->vq_index);
> - vq = vp_find_one_vq_msix(vdev, avq->vq_index, NULL, avq->name, false,
> - true, &allocated_vectors, vector_policy,
> - &vp_dev->admin_vq.info);
> + vq = vp_find_one_vq_msix(vdev, avq->vq_index, vp_modern_avq_done,
> + avq->name, false, true, &allocated_vectors,
> + vector_policy, &vp_dev->admin_vq.info);
> if (IS_ERR(vq)) {
> err = PTR_ERR(vq);
> goto error_find;
> @@ -486,8 +488,9 @@ static int vp_find_vqs_intx(struct virtio_device *vdev, unsigned int nvqs,
> if (!avq_num)
> return 0;
> sprintf(avq->name, "avq.%u", avq->vq_index);
> - vq = vp_setup_vq(vdev, queue_idx++, NULL, avq->name, false,
> - VIRTIO_MSI_NO_VECTOR, &vp_dev->admin_vq.info);
> + vq = vp_setup_vq(vdev, queue_idx++, vp_modern_avq_done, avq->name,
> + false, VIRTIO_MSI_NO_VECTOR,
> + &vp_dev->admin_vq.info);
> if (IS_ERR(vq)) {
> err = PTR_ERR(vq);
> goto out_del_vqs;
> diff --git a/drivers/virtio/virtio_pci_common.h b/drivers/virtio/virtio_pci_common.h
> index de59bb06ec3c..90df381fbbcf 100644
> --- a/drivers/virtio/virtio_pci_common.h
> +++ b/drivers/virtio/virtio_pci_common.h
> @@ -47,6 +47,8 @@ struct virtio_pci_admin_vq {
> struct virtio_pci_vq_info *info;
> /* serializing admin commands execution. */
> struct mutex cmd_lock;
> + /* Protects virtqueue access. */
> + spinlock_t lock;
> u64 supported_cmds;
> /* Name of the admin queue: avq.$vq_index. */
> char name[10];
> @@ -178,6 +180,7 @@ struct virtio_device *virtio_pci_vf_get_pf_dev(struct pci_dev *pdev);
> #define VIRTIO_ADMIN_CMD_BITMAP 0
> #endif
>
> +void vp_modern_avq_done(struct virtqueue *vq);
> int vp_modern_admin_cmd_exec(struct virtio_device *vdev,
> struct virtio_admin_cmd *cmd);
>
> diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> index 0fd344d1eaf9..608df3263df1 100644
> --- a/drivers/virtio/virtio_pci_modern.c
> +++ b/drivers/virtio/virtio_pci_modern.c
> @@ -53,6 +53,23 @@ static bool vp_is_avq(struct virtio_device *vdev, unsigned int index)
> return index == vp_dev->admin_vq.vq_index;
> }
>
> +void vp_modern_avq_done(struct virtqueue *vq)
> +{
> + struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
> + struct virtio_pci_admin_vq *admin_vq = &vp_dev->admin_vq;
> + struct virtio_admin_cmd *cmd;
> + unsigned long flags;
> + unsigned int len;
> +
> + spin_lock_irqsave(&admin_vq->lock, flags);
> + do {
> + virtqueue_disable_cb(vq);
> + while ((cmd = virtqueue_get_buf(vq, &len)))
> + complete(&cmd->completion);
> + } while (!virtqueue_enable_cb(vq));
> + spin_unlock_irqrestore(&admin_vq->lock, flags);
> +}
> +
> static int virtqueue_exec_admin_cmd(struct virtio_pci_admin_vq *admin_vq,
> u16 opcode,
> struct scatterlist **sgs,
> @@ -61,7 +78,8 @@ static int virtqueue_exec_admin_cmd(struct virtio_pci_admin_vq *admin_vq,
> struct virtio_admin_cmd *cmd)
> {
> struct virtqueue *vq;
> - int ret, len;
> + unsigned long flags;
> + int ret;
>
> vq = admin_vq->info->vq;
> if (!vq)
> @@ -72,21 +90,33 @@ static int virtqueue_exec_admin_cmd(struct virtio_pci_admin_vq *admin_vq,
> !((1ULL << opcode) & admin_vq->supported_cmds))
> return -EOPNOTSUPP;
>
> - ret = virtqueue_add_sgs(vq, sgs, out_num, in_num, cmd, GFP_KERNEL);
> - if (ret < 0)
> - return -EIO;
> + init_completion(&cmd->completion);
>
> - if (unlikely(!virtqueue_kick(vq)))
> +again:
> + if (virtqueue_is_broken(vq))
> return -EIO;
>
> - while (!virtqueue_get_buf(vq, &len) &&
> - !virtqueue_is_broken(vq))
> - cpu_relax();
> + spin_lock_irqsave(&admin_vq->lock, flags);
> + ret = virtqueue_add_sgs(vq, sgs, out_num, in_num, cmd, GFP_KERNEL);
> + if (ret < 0) {
> + if (ret == -ENOSPC) {
> + spin_unlock_irqrestore(&admin_vq->lock, flags);
> + cpu_relax();
> + goto again;
> + }
> + goto unlock_err;
> + }
> + if (!virtqueue_kick(vq))
> + goto unlock_err;
> + spin_unlock_irqrestore(&admin_vq->lock, flags);
>
> - if (virtqueue_is_broken(vq))
> - return -EIO;
> + wait_for_completion(&cmd->completion);
>
> - return 0;
> + return cmd->ret;
> +
> +unlock_err:
> + spin_unlock_irqrestore(&admin_vq->lock, flags);
> + return -EIO;
> }
>
> int vp_modern_admin_cmd_exec(struct virtio_device *vdev,
> @@ -209,6 +239,25 @@ static void vp_modern_avq_activate(struct virtio_device *vdev)
> virtio_pci_admin_cmd_list_init(vdev);
> }
>
> +static void vp_modern_avq_cleanup(struct virtio_device *vdev)
> +{
> + struct virtio_pci_device *vp_dev = to_vp_device(vdev);
> + struct virtio_admin_cmd *cmd;
> + struct virtqueue *vq;
> +
> + if (!virtio_has_feature(vdev, VIRTIO_F_ADMIN_VQ))
> + return;
> +
> + vq = vp_dev->vqs[vp_dev->admin_vq.vq_index]->vq;
> + if (!vq)
> + return;
> +
> + while ((cmd = virtqueue_detach_unused_buf(vq))) {
> + cmd->ret = -EIO;
> + complete(&cmd->completion);
> + }
> +}
> +
I think surprise removal is still broken with this.
You need to add a callback and signal the completion.
--
MST
