Wed, Jul 10, 2024 at 03:06:57PM CEST, mst@xxxxxxxxxx wrote:
>On Wed, Jul 10, 2024 at 03:03:33PM +0200, Jiri Pirko wrote:
>> Wed, Jul 10, 2024 at 01:47:22PM CEST, mst@xxxxxxxxxx wrote:
>> >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.
>>
>> Why do you think so? I will drain the remaining buffers from the queue
>> and complete them all. What's missing?
>
>You have this:
>
>> >> + wait_for_completion(&cmd->completion);
>
>if surprise removal triggers after you submitted command
>but before it was used, no callback triggers and so no
>completion either.
Well. In that case
virtio_pci_remove()
-> unregister_virtio_device()
-> device_unregister()
-> virtnet_remove()
-> remove_vq_common()
-> virtio_reset_device()
-> vp_reset()
-> vp_modern_avq_cleanup()
which goes over these cmds and does complete
them all. See vp_modern_avq_cleanup() above.
What am I missing?
>
>
>>
>> >You need to add a callback and signal the completion.
>>
>> Callback to what?
>
>for example, remove callback can signal completion.
>
>
>>
>>
>>
>> >
>> >--
>> >MST
>> >
>
