Current virtqueue_add API implementation is based on the scatterlist
struct, which uses kaddr. This is inadequate to all the use case of
vring. For example:
- Some usages don't use IOMMU, in this case the user can directly pass
in a physical address in hand, instead of going through the sg
implementation (e.g. the VIRTIO_BALLOON_F_SG feature)
- Sometimes, a guest physical page may not have a kaddr (e.g. high
memory) but need to use vring (e.g. the VIRTIO_BALLOON_F_FREE_PAGE_VQ
feature)
The new API virtqueue_add_one_desc enables the caller to assign a vring
desc with a physical address and len. Also, factor out the common code
with virtqueue_add in vring_set_avail.
Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
drivers/virtio/virtio_ring.c | 94 +++++++++++++++++++++++++++++++++++---------
include/linux/virtio.h | 6 +++
2 files changed, 81 insertions(+), 19 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index eb30f3e..0b87123 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -257,6 +257,79 @@ static struct vring_desc *alloc_indirect(struct virtqueue *_vq,
return desc;
}
+static void vring_set_avail(struct virtqueue *_vq,
+ unsigned int i)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ unsigned int avail;
+
+ avail = vq->avail_idx_shadow & (vq->vring.num - 1);
+ vq->vring.avail->ring[avail] = cpu_to_virtio16(_vq->vdev, i);
+
+ /*
+ * Descriptors and available array need to be set before we expose the
+ * new available array entries.
+ */
+ virtio_wmb(vq->weak_barriers);
+ vq->avail_idx_shadow++;
+ vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev,
+ vq->avail_idx_shadow);
+ vq->num_added++;
+
+ pr_debug("Added buffer head %i to %p\n", i, vq);
+
+ /*
+ * This is very unlikely, but theoretically possible. Kick
+ * just in case.
+ */
+ if (unlikely(vq->num_added == (1 << 16) - 1))
+ virtqueue_kick(_vq);
+}
+
+int virtqueue_add_one_desc(struct virtqueue *_vq,
+ uint64_t addr,
+ uint32_t len,
+ bool in_desc,
+ void *data)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ struct vring_desc *desc;
+ unsigned int i;
+
+ START_USE(vq);
+ BUG_ON(data == NULL);
+
+ if (unlikely(vq->broken)) {
+ END_USE(vq);
+ return -EIO;
+ }
+
+ if (_vq->num_free < 1) {
+ END_USE(vq);
+ return -ENOSPC;
+ }
+
+ i = vq->free_head;
+ desc = &vq->vring.desc[i];
+ desc->addr = cpu_to_virtio64(_vq->vdev, addr);
+ desc->len = cpu_to_virtio32(_vq->vdev, len);
+ if (in_desc)
+ desc->flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_WRITE);
+ else
+ desc->flags = 0;
+ vq->desc_state[i].data = data;
+ vq->desc_state[i].indir_desc = NULL;
+ vq->free_head = virtio16_to_cpu(_vq->vdev, vq->vring.desc[i].next);
+ _vq->num_free--;
+
+ vring_set_avail(_vq, i);
+
+ END_USE(vq);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(virtqueue_add_one_desc);
+
static inline int virtqueue_add(struct virtqueue *_vq,
struct scatterlist *sgs[],
unsigned int total_sg,
@@ -269,7 +342,7 @@ static inline int virtqueue_add(struct virtqueue *_vq,
struct vring_virtqueue *vq = to_vvq(_vq);
struct scatterlist *sg;
struct vring_desc *desc;
- unsigned int i, n, avail, descs_used, uninitialized_var(prev), err_idx;
+ unsigned int i, n, descs_used, uninitialized_var(prev), err_idx;
int head;
bool indirect;
@@ -395,26 +468,9 @@ static inline int virtqueue_add(struct virtqueue *_vq,
else
vq->desc_state[head].indir_desc = ctx;
- /* Put entry in available array (but don't update avail->idx until they
- * do sync). */
- avail = vq->avail_idx_shadow & (vq->vring.num - 1);
- vq->vring.avail->ring[avail] = cpu_to_virtio16(_vq->vdev, head);
-
- /* Descriptors and available array need to be set before we expose the
- * new available array entries. */
- virtio_wmb(vq->weak_barriers);
- vq->avail_idx_shadow++;
- vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev, vq->avail_idx_shadow);
- vq->num_added++;
-
- pr_debug("Added buffer head %i to %p\n", head, vq);
+ vring_set_avail(_vq, head);
END_USE(vq);
- /* This is very unlikely, but theoretically possible. Kick
- * just in case. */
- if (unlikely(vq->num_added == (1 << 16) - 1))
- virtqueue_kick(_vq);
-
return 0;
unmap_release:
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 988c735..1d89996 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -35,6 +35,12 @@ struct virtqueue {
void *priv;
};
+int virtqueue_add_one_desc(struct virtqueue *_vq,
+ uint64_t addr,
+ uint32_t len,
+ bool in_desc,
+ void *data);
+
int virtqueue_add_outbuf(struct virtqueue *vq,
struct scatterlist sg[], unsigned int num,
void *data,
--
2.7.4
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