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 | 105 ++++++++++++++++++++++++++++++++---
include/linux/virtio.h | 9 ++-
2 files changed, 103 insertions(+), 11 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index cdc4349f6066..cbc22daae7e1 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1695,8 +1695,85 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq)
return needs_kick;
}
+static void detach_cursor_init_packed(struct vring_virtqueue *vq,
+ struct virtqueue_detach_cursor *cursor, u16 id)
+{
+ struct vring_desc_state_packed *state = NULL;
+ u32 len;
+
+ state = &vq->packed.desc_state[id];
+
+ /* Clear data ptr. */
+ state->data = NULL;
+
+ vq->packed.desc_extra[state->last].next = vq->free_head;
+ vq->free_head = id;
+ vq->vq.num_free += state->num;
+
+ /* init cursor */
+ cursor->curr = id;
+ cursor->done = 0;
+ cursor->pos = 0;
+
+ if (vq->packed.desc_extra[id].flags & VRING_DESC_F_INDIRECT) {
+ len = vq->split.desc_extra[id].len;
+
+ cursor->num = len / sizeof(struct vring_packed_desc);
+ cursor->indirect = true;
+
+ vring_unmap_extra_packed(vq, &vq->packed.desc_extra[id]);
+ } else {
+ cursor->num = state->num;
+ cursor->indirect = false;
+ }
+}
+
+static int virtqueue_detach_packed(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);
+
+ if (unlikely(cursor->done))
+ return -EINVAL;
+
+ if (!cursor->indirect) {
+ struct vring_desc_extra *extra;
+
+ extra = &vq->packed.desc_extra[cursor->curr];
+ cursor->curr = extra->next;
+
+ *addr = extra->addr;
+ *len = extra->len;
+ *dir = (extra->flags & VRING_DESC_F_WRITE) ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
+
+ if (++cursor->pos == cursor->num) {
+ cursor->done = true;
+ return 0;
+ }
+ } else {
+ struct vring_packed_desc *indir_desc, *desc;
+ u16 flags;
+
+ indir_desc = vq->packed.desc_state[cursor->curr].indir_desc;
+ desc = &indir_desc[cursor->pos];
+
+ flags = le16_to_cpu(desc->flags);
+ *addr = le64_to_cpu(desc->addr);
+ *len = le32_to_cpu(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 -EAGAIN;
+}
+
static void detach_buf_packed(struct vring_virtqueue *vq,
- unsigned int id, void **ctx)
+ unsigned int id)
{
struct vring_desc_state_packed *state = NULL;
struct vring_packed_desc *desc;
@@ -1736,8 +1813,6 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
}
kfree(desc);
state->indir_desc = NULL;
- } else if (ctx) {
- *ctx = state->indir_desc;
}
}
@@ -1768,7 +1843,8 @@ static bool more_used_packed(const struct vring_virtqueue *vq)
static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq,
unsigned int *len,
- void **ctx)
+ void **ctx,
+ struct virtqueue_detach_cursor *cursor)
{
struct vring_virtqueue *vq = to_vvq(_vq);
u16 last_used, id, last_used_idx;
@@ -1808,7 +1884,14 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq,
/* detach_buf_packed clears data, so grab it now. */
ret = vq->packed.desc_state[id].data;
- detach_buf_packed(vq, id, ctx);
+
+ if (!vq->indirect && ctx)
+ *ctx = vq->packed.desc_state[id].indir_desc;
+
+ if (vq->premapped)
+ detach_cursor_init_packed(vq, cursor, id);
+ else
+ detach_buf_packed(vq, id);
last_used += vq->packed.desc_state[id].num;
if (unlikely(last_used >= vq->packed.vring.num)) {
@@ -1960,7 +2043,8 @@ static bool virtqueue_enable_cb_delayed_packed(struct virtqueue *_vq)
return true;
}
-static void *virtqueue_detach_unused_buf_packed(struct virtqueue *_vq)
+static void *virtqueue_detach_unused_buf_packed(struct virtqueue *_vq,
+ struct virtqueue_detach_cursor *cursor)
{
struct vring_virtqueue *vq = to_vvq(_vq);
unsigned int i;
@@ -1973,7 +2057,10 @@ static void *virtqueue_detach_unused_buf_packed(struct virtqueue *_vq)
continue;
/* detach_buf clears data, so grab it now. */
buf = vq->packed.desc_state[i].data;
- detach_buf_packed(vq, i, NULL);
+ if (vq->premapped)
+ detach_cursor_init_packed(vq, cursor, i);
+ else
+ detach_buf_packed(vq, i);
END_USE(vq);
return buf;
}
@@ -2458,7 +2545,7 @@ 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) :
+ return vq->packed_ring ? virtqueue_get_buf_ctx_packed(_vq, len, ctx, NULL) :
virtqueue_get_buf_ctx_split(_vq, len, ctx, NULL);
}
EXPORT_SYMBOL_GPL(virtqueue_get_buf_ctx);
@@ -2590,7 +2677,7 @@ 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) :
+ return vq->packed_ring ? virtqueue_detach_unused_buf_packed(_vq, NULL) :
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 eb4a4e4329aa..7f137c7a9034 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -43,8 +43,13 @@ struct virtqueue_detach_cursor {
unsigned done:1;
unsigned hole:14;
- /* for split head */
- unsigned head:16;
+ union {
+ /* for split head */
+ unsigned head:16;
+
+ /* for packed id */
+ unsigned curr:16;
+ };
unsigned num:16;
unsigned pos:16;
};
--
2.32.0.3.g01195cf9f
