Re: [Qemu-devel] [[RFC v3 03/12] virtio: init memory cache for packed ring

[Jason Wang <jasowang@redhat.com>]

On 2018年10月11日 22:08, wexu@redhat.com wrote:
> From: Wei Xu <wexu@redhat.com>
>
> Expand 1.0 by adding offset calculation accordingly.

This is only part of what this patch did and I suggest to another patch 
to do this.

>
> Signed-off-by: Wei Xu <wexu@redhat.com>
> ---
>   hw/virtio/vhost.c          | 16 ++++++++--------
>   hw/virtio/virtio.c         | 35 +++++++++++++++++++++++------------
>   include/hw/virtio/virtio.h |  4 ++--
>   3 files changed, 33 insertions(+), 22 deletions(-)
>
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 569c405..9df2da3 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -996,14 +996,14 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
>           r = -ENOMEM;
>           goto fail_alloc_desc;
>       }
> -    vq->avail_size = s = l = virtio_queue_get_avail_size(vdev, idx);
> +    vq->avail_size = s = l = virtio_queue_get_driver_size(vdev, idx);

Let's try to use a more consistent name. E.g either use avail/used or 
driver/device.

I prefer to use avail/used, it can save lots of unnecessary changes.

>       vq->avail_phys = a = virtio_queue_get_avail_addr(vdev, idx);
>       vq->avail = vhost_memory_map(dev, a, &l, 0);
>       if (!vq->avail || l != s) {
>           r = -ENOMEM;
>           goto fail_alloc_avail;
>       }
> -    vq->used_size = s = l = virtio_queue_get_used_size(vdev, idx);
> +    vq->used_size = s = l = virtio_queue_get_device_size(vdev, idx);
>       vq->used_phys = a = virtio_queue_get_used_addr(vdev, idx);
>       vq->used = vhost_memory_map(dev, a, &l, 1);
>       if (!vq->used || l != s) {
> @@ -1051,10 +1051,10 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
>   fail_vector:
>   fail_kick:
>   fail_alloc:
> -    vhost_memory_unmap(dev, vq->used, virtio_queue_get_used_size(vdev, idx),
> +    vhost_memory_unmap(dev, vq->used, virtio_queue_get_device_size(vdev, idx),
>                          0, 0);
>   fail_alloc_used:
> -    vhost_memory_unmap(dev, vq->avail, virtio_queue_get_avail_size(vdev, idx),
> +    vhost_memory_unmap(dev, vq->avail, virtio_queue_get_driver_size(vdev, idx),
>                          0, 0);
>   fail_alloc_avail:
>       vhost_memory_unmap(dev, vq->desc, virtio_queue_get_desc_size(vdev, idx),
> @@ -1101,10 +1101,10 @@ static void vhost_virtqueue_stop(struct vhost_dev *dev,
>                                                   vhost_vq_index);
>       }
>   
> -    vhost_memory_unmap(dev, vq->used, virtio_queue_get_used_size(vdev, idx),
> -                       1, virtio_queue_get_used_size(vdev, idx));
> -    vhost_memory_unmap(dev, vq->avail, virtio_queue_get_avail_size(vdev, idx),
> -                       0, virtio_queue_get_avail_size(vdev, idx));
> +    vhost_memory_unmap(dev, vq->used, virtio_queue_get_device_size(vdev, idx),
> +                       1, virtio_queue_get_device_size(vdev, idx));
> +    vhost_memory_unmap(dev, vq->avail, virtio_queue_get_driver_size(vdev, idx),
> +                       0, virtio_queue_get_driver_size(vdev, idx));
>       vhost_memory_unmap(dev, vq->desc, virtio_queue_get_desc_size(vdev, idx),
>                          0, virtio_queue_get_desc_size(vdev, idx));
>   }
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 500eecf..bfb3364 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -162,11 +162,8 @@ static void virtio_init_region_cache(VirtIODevice *vdev, int n)
>       VRingMemoryRegionCaches *old = vq->vring.caches;
>       VRingMemoryRegionCaches *new = NULL;
>       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) {
>           goto out_no_cache;
> @@ -174,13 +171,13 @@ static void virtio_init_region_cache(VirtIODevice *vdev, int n)
>       new = g_new0(VRingMemoryRegionCaches, 1);
>       size = virtio_queue_get_desc_size(vdev, n);
>       len = address_space_cache_init(&new->desc, vdev->dma_as,
> -                                   addr, size, false);
> +                                   addr, size, true);

This looks wrong, for split virtqueue, descriptor ring is read only.

>       if (len < size) {
>           virtio_error(vdev, "Cannot map desc");
>           goto err_desc;
>       }
>   
> -    size = virtio_queue_get_used_size(vdev, n) + event_size;
> +    size = virtio_queue_get_device_size(vdev, n);
>       len = address_space_cache_init(&new->used, vdev->dma_as,
>                                      vq->vring.used, size, true);
>       if (len < size) {
> @@ -188,7 +185,7 @@ 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_driver_size(vdev, n);
>       len = address_space_cache_init(&new->avail, vdev->dma_as,
>                                      vq->vring.avail, size, false);
>       if (len < size) {
> @@ -2339,16 +2336,30 @@ hwaddr virtio_queue_get_desc_size(VirtIODevice *vdev, int n)
>       return sizeof(VRingDesc) * vdev->vq[n].vring.num;
>   }
>   
> -hwaddr virtio_queue_get_avail_size(VirtIODevice *vdev, int n)
> +hwaddr virtio_queue_get_driver_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;

I tend to move this to an independent patch.

Thanks

> +    }
>   }
>   
> -hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, int n)
> +hwaddr virtio_queue_get_device_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)
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index 9c1fa07..e323e76 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -270,8 +270,8 @@ hwaddr virtio_queue_get_desc_addr(VirtIODevice *vdev, int n);
>   hwaddr virtio_queue_get_avail_addr(VirtIODevice *vdev, int n);
>   hwaddr virtio_queue_get_used_addr(VirtIODevice *vdev, int n);
>   hwaddr virtio_queue_get_desc_size(VirtIODevice *vdev, int n);
> -hwaddr virtio_queue_get_avail_size(VirtIODevice *vdev, int n);
> -hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, int n);
> +hwaddr virtio_queue_get_driver_size(VirtIODevice *vdev, int n);
> +hwaddr virtio_queue_get_device_size(VirtIODevice *vdev, int n);
>   uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n);
>   void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx);
>   void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n);