Under the premapped mode, the driver needs to unmap the DMA address
after receiving the buffer. The virtio core records the DMA address,
so the driver needs a way to get the dma info from the virtio core.
A straightforward approach is to pass an array to the virtio core when
calling virtqueue_get_buf(). However, it is not feasible when there are
multiple DMA addresses in the descriptor chain, and the array size is
unknown.
To solve this problem, a helper be introduced. After calling
virtqueue_get_buf(), the driver can call the helper to
retrieve a dma info. If the helper function returns -EAGAIN, it means
that there are more DMA addresses to be processed, and the driver should
call the helper function again. To keep track of the current position in
the chain, a cursor must be passed to the helper function, which is
initialized by virtqueue_get_buf().
Some processes are done inside this helper, so this helper MUST be
called under the premapped mode.
Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
---
drivers/virtio/virtio_ring.c | 118 ++++++++++++++++++++++++++++++++---
include/linux/virtio.h | 11 ++++
2 files changed, 119 insertions(+), 10 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index dc109fbc05a5..cdc4349f6066 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -754,8 +754,95 @@ static bool virtqueue_kick_prepare_split(struct virtqueue *_vq)
return needs_kick;
}
-static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
- void **ctx)
+static void detach_cursor_init_split(struct vring_virtqueue *vq,
+ struct virtqueue_detach_cursor *cursor, u16 head)
+{
+ struct vring_desc_extra *extra;
+
+ extra = &vq->split.desc_extra[head];
+
+ /* Clear data ptr. */
+ vq->split.desc_state[head].data = NULL;
+
+ cursor->head = head;
+ cursor->done = 0;
+
+ if (extra->flags & VRING_DESC_F_INDIRECT) {
+ cursor->num = extra->len / sizeof(struct vring_desc);
+ cursor->indirect = true;
+ cursor->pos = 0;
+
+ vring_unmap_one_split(vq, head);
+
+ extra->next = vq->free_head;
+
+ vq->free_head = head;
+
+ /* Plus final descriptor */
+ vq->vq.num_free++;
+
+ } else {
+ cursor->indirect = false;
+ cursor->pos = head;
+ }
+}
+
+static int virtqueue_detach_split(struct virtqueue *_vq, struct virtqueue_detach_cursor *cursor,
+ dma_addr_t *addr, u32 *len, enum dma_data_direction *dir)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ __virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
+ int rc = -EAGAIN;
+
+ if (unlikely(cursor->done))
+ return -EINVAL;
+
+ if (!cursor->indirect) {
+ struct vring_desc_extra *extra;
+ unsigned int i;
+
+ i = cursor->pos;
+
+ extra = &vq->split.desc_extra[i];
+
+ if (vq->split.vring.desc[i].flags & nextflag) {
+ cursor->pos = extra->next;
+ } else {
+ extra->next = vq->free_head;
+ vq->free_head = cursor->head;
+ cursor->done = true;
+ rc = 0;
+ }
+
+ *addr = extra->addr;
+ *len = extra->len;
+ *dir = (extra->flags & VRING_DESC_F_WRITE) ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
+
+ vq->vq.num_free++;
+
+ } else {
+ struct vring_desc *indir_desc, *desc;
+ u16 flags;
+
+ indir_desc = vq->split.desc_state[cursor->head].indir_desc;
+ desc = &indir_desc[cursor->pos];
+
+ flags = virtio16_to_cpu(vq->vq.vdev, desc->flags);
+ *addr = virtio64_to_cpu(vq->vq.vdev, desc->addr);
+ *len = virtio32_to_cpu(vq->vq.vdev, desc->len);
+ *dir = (flags & VRING_DESC_F_WRITE) ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
+
+ if (++cursor->pos == cursor->num) {
+ kfree(indir_desc);
+ cursor->done = true;
+ return 0;
+ }
+ }
+
+ return rc;
+}
+
+static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head)
{
unsigned int i, j;
__virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
@@ -799,8 +886,6 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
kfree(indir_desc);
vq->split.desc_state[head].indir_desc = NULL;
- } else if (ctx) {
- *ctx = vq->split.desc_state[head].indir_desc;
}
}
@@ -812,7 +897,8 @@ static bool more_used_split(const struct vring_virtqueue *vq)
static void *virtqueue_get_buf_ctx_split(struct virtqueue *_vq,
unsigned int *len,
- void **ctx)
+ void **ctx,
+ struct virtqueue_detach_cursor *cursor)
{
struct vring_virtqueue *vq = to_vvq(_vq);
void *ret;
@@ -852,7 +938,15 @@ static void *virtqueue_get_buf_ctx_split(struct virtqueue *_vq,
/* detach_buf_split clears data, so grab it now. */
ret = vq->split.desc_state[i].data;
- detach_buf_split(vq, i, ctx);
+
+ if (!vq->indirect && ctx)
+ *ctx = vq->split.desc_state[i].indir_desc;
+
+ if (vq->premapped)
+ detach_cursor_init_split(vq, cursor, i);
+ else
+ detach_buf_split(vq, i);
+
vq->last_used_idx++;
/* If we expect an interrupt for the next entry, tell host
* by writing event index and flush out the write before
@@ -961,7 +1055,8 @@ static bool virtqueue_enable_cb_delayed_split(struct virtqueue *_vq)
return true;
}
-static void *virtqueue_detach_unused_buf_split(struct virtqueue *_vq)
+static void *virtqueue_detach_unused_buf_split(struct virtqueue *_vq,
+ struct virtqueue_detach_cursor *cursor)
{
struct vring_virtqueue *vq = to_vvq(_vq);
unsigned int i;
@@ -974,7 +1069,10 @@ static void *virtqueue_detach_unused_buf_split(struct virtqueue *_vq)
continue;
/* detach_buf_split clears data, so grab it now. */
buf = vq->split.desc_state[i].data;
- detach_buf_split(vq, i, NULL);
+ if (vq->premapped)
+ detach_cursor_init_split(vq, cursor, i);
+ else
+ detach_buf_split(vq, i);
vq->split.avail_idx_shadow--;
vq->split.vring.avail->idx = cpu_to_virtio16(_vq->vdev,
vq->split.avail_idx_shadow);
@@ -2361,7 +2459,7 @@ void *virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len,
struct vring_virtqueue *vq = to_vvq(_vq);
return vq->packed_ring ? virtqueue_get_buf_ctx_packed(_vq, len, ctx) :
- virtqueue_get_buf_ctx_split(_vq, len, ctx);
+ virtqueue_get_buf_ctx_split(_vq, len, ctx, NULL);
}
EXPORT_SYMBOL_GPL(virtqueue_get_buf_ctx);
@@ -2493,7 +2591,7 @@ void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
struct vring_virtqueue *vq = to_vvq(_vq);
return vq->packed_ring ? virtqueue_detach_unused_buf_packed(_vq) :
- virtqueue_detach_unused_buf_split(_vq);
+ virtqueue_detach_unused_buf_split(_vq, NULL);
}
EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf);
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 1fc0e1023bd4..eb4a4e4329aa 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -38,6 +38,17 @@ struct virtqueue {
void *priv;
};
+struct virtqueue_detach_cursor {
+ unsigned indirect:1;
+ unsigned done:1;
+ unsigned hole:14;
+
+ /* for split head */
+ unsigned head:16;
+ unsigned num:16;
+ unsigned pos:16;
+};
+
int virtqueue_add_outbuf(struct virtqueue *vq,
struct scatterlist sg[], unsigned int num,
void *data,
--
2.32.0.3.g01195cf9f
