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virtio_ring: introduce helper for indirect feature 

Introduce a helper to check whether we will use indirect
feature. It will be used by packed ring too.

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Tiwei Bie 2018-11-21 18:03:23 +08:00 committed by David S. Miller
parent 4d6a105eb5
commit 2f18c2d153
1 changed files with 13 additions and 3 deletions
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16
drivers/virtio/virtio_ring.c
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@ -145,6 +145,18 @@ struct vring_virtqueue {
#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
static inline bool virtqueue_use_indirect(struct virtqueue *_vq,
unsigned int total_sg)
{
struct vring_virtqueue *vq = to_vvq(_vq);
/*
* If the host supports indirect descriptor tables, and we have multiple
* buffers, then go indirect. FIXME: tune this threshold
*/
return (vq->indirect && total_sg > 1 && vq->vq.num_free);
}
/*
* Modern virtio devices have feature bits to specify whether they need a
* quirk and bypass the IOMMU. If not there, just use the DMA API.
@ -324,9 +336,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
head = vq->free_head;
/* If the host supports indirect descriptor tables, and we have multiple
* buffers, then go indirect. FIXME: tune this threshold */
if (vq->indirect && total_sg > 1 && vq->vq.num_free)
if (virtqueue_use_indirect(_vq, total_sg))
desc = alloc_indirect_split(_vq, total_sg, gfp);
else {
desc = NULL;