[PATCH vhost v6 07/10] virtio: find_vqs: add new parameter premapped

[Xuan Zhuo]

If the premapped mode is enabled, the dma array(struct vring_desc_dma) of
virtio core will not be allocated. That is judged when find_vqs() is
called. To avoid allocating dma array in find_vqs() and releasing it
immediately by virtqueue_set_dma_premapped(). This patch introduces a
new parameter to find_vqs(). Then we can judge should we allocate the
dma array(struct vring_desc_dma) or not inside find_vqs().

The driver must check the premapped mode of every vq after find_vqs().

Signed-off-by: Xuan Zhuo <xuanz...@linux.alibaba.com>
---
 drivers/virtio/virtio_ring.c  | 4 ++--
 include/linux/virtio_config.h | 3 +++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 08e4f6e1d722..bbdeab3a9648 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2148,7 +2148,7 @@ static struct virtqueue 
*vring_create_virtqueue_packed(struct virtio_device *vde
        vq->packed_ring = true;
        vq->dma_dev = dma_dev;
        vq->use_dma_api = vring_use_dma_api(vdev);
-       vq->premapped = false;
+       vq->premapped = vq->use_dma_api && cfg_vq_get(cfg, vq, premapped);
 
        vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) &&
                !cfg_vq_get(cfg, vq, ctx);
@@ -2696,7 +2696,7 @@ static struct virtqueue *__vring_new_virtqueue(struct 
virtio_device *vdev,
 #endif
        vq->dma_dev = tp_cfg->dma_dev;
        vq->use_dma_api = vring_use_dma_api(vdev);
-       vq->premapped = false;
+       vq->premapped = vq->use_dma_api && cfg_vq_get(cfg, vq, premapped);
 
        vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) &&
                !cfg_vq_get(cfg, vq, ctx);
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 370e79df50c4..80b7974ca9ff 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -29,6 +29,8 @@ typedef void vq_callback_t(struct virtqueue *);
  * @ctx: (optional) array of context. If the value of the vq in the array
  *     is true, the driver can pass ctx to virtio core when adding bufs to
  *     virtqueue.
+ * @premapped: (optional) array of premapped. If the value of the vq in the
+ *      array is true, the vq will try to enable premapped mode.
  * @desc: desc for interrupts
  */
 struct virtio_vq_config {
@@ -38,6 +40,7 @@ struct virtio_vq_config {
        vq_callback_t      **callbacks;
        const char         **names;
        const bool          *ctx;
+       const bool          *premapped;
        struct irq_affinity *desc;
 };
 
-- 
2.32.0.3.g01195cf9f