[PATCH vhost v1 11/19] 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 <xuanzhuo at linux.alibaba.com>
---
 drivers/virtio/virtio_ring.c  | 4 ++--
 include/linux/virtio_config.h | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index d09572dadd9e..5a9d8cb9ab0e 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2145,7 +2145,7 @@ 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, premapped);
 
 	vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) &&
 		!cfg_vq_get(cfg, ctx);
@@ -2687,7 +2687,7 @@ 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, premapped);
 
 	vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) &&
 		!cfg_vq_get(cfg, ctx);
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index ffe18c3815fc..18919d1384bb 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -105,6 +105,7 @@ 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