Re: [RFC PATCH v4 12/20] virtio: Add vhost_shadow_vq_get_vring_addr

[Jason Wang]

在 2021/10/1 下午3:05, Eugenio Pérez 写道:
> It reports the shadow virtqueue address from qemu virtual address space


I think both the title and commit log needs to more tweaks. Looking at 
the codes, what id does is actually introduce vring into svq.


> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>   hw/virtio/vhost-shadow-virtqueue.h |  4 +++
>   hw/virtio/vhost-shadow-virtqueue.c | 50 ++++++++++++++++++++++++++++++
>   2 files changed, 54 insertions(+)
>
> diff --git a/hw/virtio/vhost-shadow-virtqueue.h 
> b/hw/virtio/vhost-shadow-virtqueue.h
> index 237cfceb9c..2df3d117f5 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.h
> +++ b/hw/virtio/vhost-shadow-virtqueue.h
> @@ -16,6 +16,10 @@ typedef struct VhostShadowVirtqueue VhostShadowVirtqueue;
>   
>   EventNotifier *vhost_svq_get_svq_call_notifier(VhostShadowVirtqueue *svq);
>   void vhost_svq_set_guest_call_notifier(VhostShadowVirtqueue *svq, int 
> call_fd);
> +void vhost_svq_get_vring_addr(const VhostShadowVirtqueue *svq,
> +                              struct vhost_vring_addr *addr);
> +size_t vhost_svq_driver_area_size(const VhostShadowVirtqueue *svq);
> +size_t vhost_svq_device_area_size(const VhostShadowVirtqueue *svq);
>   
>   bool vhost_svq_start(struct vhost_dev *dev, unsigned idx,
>                        VhostShadowVirtqueue *svq);
> diff --git a/hw/virtio/vhost-shadow-virtqueue.c 
> b/hw/virtio/vhost-shadow-virtqueue.c
> index 3fe129cf63..5c1899f6af 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.c
> +++ b/hw/virtio/vhost-shadow-virtqueue.c
> @@ -18,6 +18,9 @@
>   
>   /* 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 */
> @@ -38,6 +41,9 @@ typedef struct VhostShadowVirtqueue {
>   
>       /* Virtio queue shadowing */
>       VirtQueue *vq;
> +
> +    /* Virtio device */
> +    VirtIODevice *vdev;
>   } VhostShadowVirtqueue;
>   
>   /* Forward guest notifications */
> @@ -93,6 +99,35 @@ void vhost_svq_set_guest_call_notifier(VhostShadowVirtqueue 
> *svq, int call_fd)
>       event_notifier_init_fd(&svq->guest_call_notifier, call_fd);
>   }
>   
> +/*
> + * Get the shadow vq vring address.
> + * @svq Shadow virtqueue
> + * @addr Destination to store address
> + */
> +void vhost_svq_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;
> +}
> +
> +size_t vhost_svq_driver_area_size(const VhostShadowVirtqueue *svq)
> +{
> +    uint16_t vq_idx = virtio_get_queue_index(svq->vq);
> +    size_t desc_size = virtio_queue_get_desc_size(svq->vdev, vq_idx);
> +    size_t avail_size = virtio_queue_get_avail_size(svq->vdev, vq_idx);
> +
> +    return ROUND_UP(desc_size + avail_size, qemu_real_host_page_size);


Is this round up required by the spec?


> +}
> +
> +size_t vhost_svq_device_area_size(const VhostShadowVirtqueue *svq)
> +{
> +    uint16_t vq_idx = virtio_get_queue_index(svq->vq);
> +    size_t used_size = virtio_queue_get_used_size(svq->vdev, vq_idx);
> +    return ROUND_UP(used_size, qemu_real_host_page_size);
> +}
> +
>   /*
>    * Restore the vhost guest to host notifier, i.e., disables svq effect.
>    */
> @@ -178,6 +213,10 @@ void vhost_svq_stop(struct vhost_dev *dev, unsigned idx,
>   VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev *dev, int idx)
>   {
>       int vq_idx = dev->vq_index + idx;
> +    unsigned num = virtio_queue_get_num(dev->vdev, vq_idx);
> +    size_t desc_size = virtio_queue_get_desc_size(dev->vdev, vq_idx);
> +    size_t driver_size;
> +    size_t device_size;
>       g_autofree VhostShadowVirtqueue *svq = g_new0(VhostShadowVirtqueue, 1);
>       int r;
>   
> @@ -196,6 +235,15 @@ VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev *dev, int idx)
>       }
>   
>       svq->vq = virtio_get_queue(dev->vdev, vq_idx);
> +    svq->vdev = dev->vdev;
> +    driver_size = vhost_svq_driver_area_size(svq);
> +    device_size = vhost_svq_device_area_size(svq);
> +    svq->vring.num = num;
> +    svq->vring.desc = qemu_memalign(qemu_real_host_page_size, driver_size);
> +    svq->vring.avail = (void *)((char *)svq->vring.desc + desc_size);
> +    memset(svq->vring.desc, 0, driver_size);


Any reason for using the contiguous area for both desc and avail?

Thanks


> +    svq->vring.used = qemu_memalign(qemu_real_host_page_size, device_size);
> +    memset(svq->vring.used, 0, device_size);
>       event_notifier_set_handler(&svq->call_notifier,
>                                  vhost_svq_handle_call);
>       return g_steal_pointer(&svq);
> @@ -215,5 +263,7 @@ void vhost_svq_free(VhostShadowVirtqueue *vq)
>       event_notifier_cleanup(&vq->kick_notifier);
>       event_notifier_set_handler(&vq->call_notifier, NULL);
>       event_notifier_cleanup(&vq->call_notifier);
> +    qemu_vfree(vq->vring.desc);
> +    qemu_vfree(vq->vring.used);
>       g_free(vq);
>   }