Virtualization - Mar 2021 - [RFC v2 08/13] virtio: Add vhost_shadow_vq_get_vring_addr

? 2021/3/16 ??3:48, Eugenio P?rez ??:
> It reports the shadow virtqueue address from qemu virtual address space

Note that to be used by vDPA, we can't use qemu VA directly here.

>
> Signed-off-by: Eugenio P?rez <eperezma at redhat.com>
> ---
>   hw/virtio/vhost-shadow-virtqueue.h |  2 ++
>   hw/virtio/vhost-shadow-virtqueue.c | 24 +++++++++++++++++++++++-
>   2 files changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/hw/virtio/vhost-shadow-virtqueue.h
b/hw/virtio/vhost-shadow-virtqueue.h
> index 2ca4b92b12..d82c35bccf 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.h
> +++ b/hw/virtio/vhost-shadow-virtqueue.h
> @@ -19,6 +19,8 @@ typedef struct VhostShadowVirtqueue VhostShadowVirtqueue;
>   
>   void vhost_shadow_vq_mask(VhostShadowVirtqueue *svq, EventNotifier
*masked);
>   void vhost_shadow_vq_unmask(VhostShadowVirtqueue *svq);
> +void vhost_shadow_vq_get_vring_addr(const VhostShadowVirtqueue *svq,
> +                                    struct vhost_vring_addr *addr);
>   
>   bool vhost_shadow_vq_start(struct vhost_dev *dev,
>                              unsigned idx,
> diff --git a/hw/virtio/vhost-shadow-virtqueue.c
b/hw/virtio/vhost-shadow-virtqueue.c
> index b6bab438d6..1460d1d5d1 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.c
> +++ b/hw/virtio/vhost-shadow-virtqueue.c
> @@ -17,6 +17,9 @@
>   
>   /* Shadow virtqueue to relay notifications */
>   typedef struct VhostShadowVirtqueue {
> +    /* Shadow vring */
> +    struct vring vring;
> +
>       /* Shadow kick notifier, sent to vhost */
>       EventNotifier kick_notifier;
>       /* Shadow call notifier, sent to vhost */
> @@ -51,6 +54,9 @@ typedef struct VhostShadowVirtqueue {
>   
>       /* Virtio device */
>       VirtIODevice *vdev;
> +
> +    /* Descriptors copied from guest */
> +    vring_desc_t descs[];
>   } VhostShadowVirtqueue;
>   
>   /* Forward guest notifications */
> @@ -132,6 +138,19 @@ void vhost_shadow_vq_unmask(VhostShadowVirtqueue *svq)
>       qemu_event_wait(&svq->masked_notifier.is_free);
>   }
>   
> +/*
> + * Get the shadow vq vring address.
> + * @svq Shadow virtqueue
> + * @addr Destination to store address
> + */
> +void vhost_shadow_vq_get_vring_addr(const VhostShadowVirtqueue *svq,
> +                                    struct vhost_vring_addr *addr)
> +{
> +    addr->desc_user_addr = (uint64_t)svq->vring.desc;
> +    addr->avail_user_addr = (uint64_t)svq->vring.avail;
> +    addr->used_user_addr = (uint64_t)svq->vring.used;
> +}
> +
>   /*
>    * Restore the vhost guest to host notifier, i.e., disables svq effect.
>    */
> @@ -262,7 +281,9 @@ void vhost_shadow_vq_stop(struct vhost_dev *dev,
>   VhostShadowVirtqueue *vhost_shadow_vq_new(struct vhost_dev *dev, int idx)
>   {
>       int vq_idx = dev->vq_index + idx;
> -    g_autofree VhostShadowVirtqueue *svq = g_new0(VhostShadowVirtqueue,
1);
> +    unsigned num = virtio_queue_get_num(dev->vdev, vq_idx);
> +    size_t ring_size = vring_size(num, VRING_DESC_ALIGN_SIZE);
> +    g_autofree VhostShadowVirtqueue *svq = g_malloc0(sizeof(*svq) +
ring_size);
>       int r;
>   
>       r = event_notifier_init(&svq->kick_notifier, 0);
> @@ -279,6 +300,7 @@ VhostShadowVirtqueue *vhost_shadow_vq_new(struct
vhost_dev *dev, int idx)
>           goto err_init_call_notifier;
>       }
>   
> +    vring_init(&svq->vring, num, svq->descs,
VRING_DESC_ALIGN_SIZE);

We had some dicussion in the past. Exporting vring_init() is wrong but 
too late to fix (assumes a legacy split layout). Let's not depend on 
this buggy uAPI.

Thanks

>       svq->vq = virtio_get_queue(dev->vdev, vq_idx);
>       svq->vdev = dev->vdev;
>       event_notifier_set_handler(&svq->call_notifier,