Commit fa56d17b authored by Jason Wang's avatar Jason Wang Committed by Michael S. Tsirkin
Browse files

virtio_ring: factor out core logic for updating last_used_idx 



Factor out the core logic for updating last_used_idx to be reused by
the packed in order implementation.

Acked-by: default avatarEugenio Pérez <eperezma@redhat.com>
Reviewed-by: default avatarXuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Tested-by: default avatarLei Yang <leiyang@redhat.com>
Reviewed-by: default avatarEugenio Pérez <eperezma@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-17-jasowang@redhat.com>
parent c623106c

drivers/virtio/virtio_ring.c

+25 −18
Original line number Diff line number Diff line
@@ -1754,6 +1754,30 @@ static bool more_used_packed(const struct vring_virtqueue *vq) 
	return virtqueue_poll_packed(vq, READ_ONCE(vq->last_used_idx));

}



static void update_last_used_idx_packed(struct vring_virtqueue *vq,

					u16 id, u16 last_used,

					u16 used_wrap_counter)

{

	last_used += vq->packed.desc_state[id].num;

	if (unlikely(last_used >= vq->packed.vring.num)) {

		last_used -= vq->packed.vring.num;

		used_wrap_counter ^= 1;

	}



	last_used = (last_used | (used_wrap_counter << VRING_PACKED_EVENT_F_WRAP_CTR));

	WRITE_ONCE(vq->last_used_idx, last_used);



	/*

	 * If we expect an interrupt for the next entry, tell host

	 * by writing event index and flush out the write before

	 * the read in the next get_buf call.

	 */

	if (vq->packed.event_flags_shadow == VRING_PACKED_EVENT_FLAG_DESC)

		virtio_store_mb(vq->weak_barriers,

				&vq->packed.vring.driver->off_wrap,

				cpu_to_le16(vq->last_used_idx));

}



static void *virtqueue_get_buf_ctx_packed(struct vring_virtqueue *vq,

					  unsigned int *len,

					  void **ctx)
@@ -1797,24 +1821,7 @@ static void *virtqueue_get_buf_ctx_packed(struct vring_virtqueue *vq, 
	ret = vq->packed.desc_state[id].data;

	detach_buf_packed(vq, id, ctx);



	last_used += vq->packed.desc_state[id].num;

	if (unlikely(last_used >= vq->packed.vring.num)) {

		last_used -= vq->packed.vring.num;

		used_wrap_counter ^= 1;

	}



	last_used = (last_used | (used_wrap_counter << VRING_PACKED_EVENT_F_WRAP_CTR));

	WRITE_ONCE(vq->last_used_idx, last_used);



	/*

	 * If we expect an interrupt for the next entry, tell host

	 * by writing event index and flush out the write before

	 * the read in the next get_buf call.

	 */

	if (vq->packed.event_flags_shadow == VRING_PACKED_EVENT_FLAG_DESC)

		virtio_store_mb(vq->weak_barriers,

				&vq->packed.vring.driver->off_wrap,

				cpu_to_le16(vq->last_used_idx));

	update_last_used_idx_packed(vq, id, last_used, used_wrap_counter);



	LAST_ADD_TIME_INVALID(vq);