Re: [PATCH v3 06/15] virtio-pci: support queue reset

[Jason Wang]

在 2022/8/25 16:08, Kangjie Xu 写道:
> From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
>
> PCI devices support vq reset.
>
> Based on this function, the driver can adjust the size of the ring, and
> quickly recycle the buffer in the ring.
>
> The migration of the virtio devices will not happen during a reset
> operation. This is becuase the global iothread lock is held. Migration
> thread also needs the lock. As a result, when migration of virtio
> devices starts, the 'reset' status of VirtIOPCIQueue will always be 0.
> Thus, we do not need to add it in vmstate_virtio_pci_modern_queue_state.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> Signed-off-by: Kangjie Xu <kangjie.xu@linux.alibaba.com>


Acked-by: Jason Wang <jasowang@redhat.com>


> ---
>   hw/virtio/virtio-pci.c         | 15 +++++++++++++++
>   include/hw/virtio/virtio-pci.h |  5 +++++
>   2 files changed, 20 insertions(+)
>
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index a50c5a57d7..79b9e641dd 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -1251,6 +1251,9 @@ static uint64_t virtio_pci_common_read(void *opaque, 
> hwaddr addr,
>       case VIRTIO_PCI_COMMON_Q_USEDHI:
>           val = proxy->vqs[vdev->queue_sel].used[1];
>           break;
> +    case VIRTIO_PCI_COMMON_Q_RESET:
> +        val = proxy->vqs[vdev->queue_sel].reset;
> +        break;
>       default:
>           val = 0;
>       }
> @@ -1338,6 +1341,7 @@ static void virtio_pci_common_write(void *opaque, hwaddr 
> addr,
>                          ((uint64_t)proxy->vqs[vdev->queue_sel].used[1]) << 32 |
>                          proxy->vqs[vdev->queue_sel].used[0]);
>               proxy->vqs[vdev->queue_sel].enabled = 1;
> +            proxy->vqs[vdev->queue_sel].reset = 0;
>           } else {
>               virtio_error(vdev, "wrong value for queue_enable %"PRIx64, val);
>           }
> @@ -1360,6 +1364,16 @@ static void virtio_pci_common_write(void *opaque, hwaddr 
> addr,
>       case VIRTIO_PCI_COMMON_Q_USEDHI:
>           proxy->vqs[vdev->queue_sel].used[1] = val;
>           break;
> +    case VIRTIO_PCI_COMMON_Q_RESET:
> +        if (val == 1) {
> +            proxy->vqs[vdev->queue_sel].reset = 1;
> +
> +            virtio_queue_reset(vdev, vdev->queue_sel);
> +
> +            proxy->vqs[vdev->queue_sel].reset = 0;
> +            proxy->vqs[vdev->queue_sel].enabled = 0;
> +        }
> +        break;
>       default:
>           break;
>       }
> @@ -1954,6 +1968,7 @@ static void virtio_pci_reset(DeviceState *qdev)
>   
>       for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
>           proxy->vqs[i].enabled = 0;
> +        proxy->vqs[i].reset = 0;
>           proxy->vqs[i].num = 0;
>           proxy->vqs[i].desc[0] = proxy->vqs[i].desc[1] = 0;
>           proxy->vqs[i].avail[0] = proxy->vqs[i].avail[1] = 0;
> diff --git a/include/hw/virtio/virtio-pci.h b/include/hw/virtio/virtio-pci.h
> index 2446dcd9ae..938799e8f6 100644
> --- a/include/hw/virtio/virtio-pci.h
> +++ b/include/hw/virtio/virtio-pci.h
> @@ -117,6 +117,11 @@ typedef struct VirtIOPCIRegion {
>   typedef struct VirtIOPCIQueue {
>     uint16_t num;
>     bool enabled;
> +  /*
> +   * No need to migrate the reset status, because it is always 0
> +   * when the migration starts.
> +   */
> +  bool reset;
>     uint32_t desc[2];
>     uint32_t avail[2];
>     uint32_t used[2];