Re: [Qemu-devel] [RFC v2 2/8] virtio: memory cache for packed ring

[Paolo Bonzini <pbonzini@redhat.com>]

On 05/06/2018 21:07, wexu@redhat.com wrote:
> From: Wei Xu <wexu@redhat.com>
> 
> Mostly reuse memory cache with 1.0 except for the offset calculation.
> 
> Signed-off-by: Wei Xu <wexu@redhat.com>
> ---
>  hw/virtio/virtio.c | 29 ++++++++++++++++++++---------
>  1 file changed, 20 insertions(+), 9 deletions(-)
> 
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index e192a9a..f6c0689 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -150,11 +150,8 @@ static void virtio_init_region_cache(VirtIODevice *vdev, int n)
>      VRingMemoryRegionCaches *old = vq->vring.caches;
>      VRingMemoryRegionCaches *new;
>      hwaddr addr, size;
> -    int event_size;
>      int64_t len;
>  
> -    event_size = virtio_vdev_has_feature(vq->vdev, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
> -
>      addr = vq->vring.desc;
>      if (!addr) {
>          return;
> @@ -168,7 +165,7 @@ static void virtio_init_region_cache(VirtIODevice *vdev, int n)
>          goto err_desc;
>      }
>  
> -    size = virtio_queue_get_used_size(vdev, n) + event_size;
> +    size = virtio_queue_get_used_size(vdev, n);
>      len = address_space_cache_init(&new->used, vdev->dma_as,
>                                     vq->vring.used, size, true);
>      if (len < size) {
> @@ -176,7 +173,7 @@ static void virtio_init_region_cache(VirtIODevice *vdev, int n)
>          goto err_used;
>      }
>  
> -    size = virtio_queue_get_avail_size(vdev, n) + event_size;
> +    size = virtio_queue_get_avail_size(vdev, n);
>      len = address_space_cache_init(&new->avail, vdev->dma_as,
>                                     vq->vring.avail, size, false);
>      if (len < size) {
> @@ -2320,14 +2317,28 @@ hwaddr virtio_queue_get_desc_size(VirtIODevice *vdev, int n)
>  
>  hwaddr virtio_queue_get_avail_size(VirtIODevice *vdev, int n)
>  {
> -    return offsetof(VRingAvail, ring) +
> -        sizeof(uint16_t) * vdev->vq[n].vring.num;
> +    int s;
> +
> +    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> +        return sizeof(struct VRingPackedDescEvent);
> +    } else {
> +        s = virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
> +        return offsetof(VRingAvail, ring) +
> +            sizeof(uint16_t) * vdev->vq[n].vring.num + s;
> +    }
>  }
>  
>  hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, int n)
>  {
> -    return offsetof(VRingUsed, ring) +
> -        sizeof(VRingUsedElem) * vdev->vq[n].vring.num;
> +    int s;
> +
> +    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> +        return sizeof(struct VRingPackedDescEvent);
> +    } else {
> +        s = virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
> +        return offsetof(VRingUsed, ring) +
> +            sizeof(VRingUsedElem) * vdev->vq[n].vring.num + s;
> +    }
>  }
>  
>  uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
> 

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>