[PATCH net-next v3 09/13] virtio_ring: cache whether we will use DMA API

[Tiwei Bie]

Cache whether we will use DMA API, instead of doing the
check every time. We are going to check whether DMA API
is used more often in packed ring.

Signed-off-by: Tiwei Bie <tiwei....@intel.com>
---
 drivers/virtio/virtio_ring.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index d00a87909a7e..aafe1969b45e 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -86,6 +86,9 @@ struct vring_desc_state_split {
 struct vring_virtqueue {
        struct virtqueue vq;
 
+       /* Is DMA API used? */
+       bool use_dma_api;
+
        /* Can we use weak barriers? */
        bool weak_barriers;
 
@@ -262,7 +265,7 @@ static dma_addr_t vring_map_one_sg(const struct 
vring_virtqueue *vq,
                                   struct scatterlist *sg,
                                   enum dma_data_direction direction)
 {
-       if (!vring_use_dma_api(vq->vq.vdev))
+       if (!vq->use_dma_api)
                return (dma_addr_t)sg_phys(sg);
 
        /*
@@ -279,7 +282,7 @@ static dma_addr_t vring_map_single(const struct 
vring_virtqueue *vq,
                                   void *cpu_addr, size_t size,
                                   enum dma_data_direction direction)
 {
-       if (!vring_use_dma_api(vq->vq.vdev))
+       if (!vq->use_dma_api)
                return (dma_addr_t)virt_to_phys(cpu_addr);
 
        return dma_map_single(vring_dma_dev(vq),
@@ -289,7 +292,7 @@ static dma_addr_t vring_map_single(const struct 
vring_virtqueue *vq,
 static int vring_mapping_error(const struct vring_virtqueue *vq,
                               dma_addr_t addr)
 {
-       if (!vring_use_dma_api(vq->vq.vdev))
+       if (!vq->use_dma_api)
                return 0;
 
        return dma_mapping_error(vring_dma_dev(vq), addr);
@@ -305,7 +308,7 @@ static void vring_unmap_one_split(const struct 
vring_virtqueue *vq,
 {
        u16 flags;
 
-       if (!vring_use_dma_api(vq->vq.vdev))
+       if (!vq->use_dma_api)
                return;
 
        flags = virtio16_to_cpu(vq->vq.vdev, desc->flags);
@@ -1202,6 +1205,7 @@ struct virtqueue *__vring_new_virtqueue(unsigned int 
index,
        vq->broken = false;
        vq->last_used_idx = 0;
        vq->num_added = 0;
+       vq->use_dma_api = vring_use_dma_api(vdev);
        list_add_tail(&vq->vq.list, &vdev->vqs);
 #ifdef DEBUG
        vq->in_use = false;
-- 
2.14.5

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