On 07/12/2017 09:06 PM, Michael S. Tsirkin wrote:
On Wed, Jul 12, 2017 at 08:40:18PM +0800, Wei Wang wrote:
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 28b0e96..9f27101 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -57,8 +57,28 @@ int virtqueue_add_sgs(struct virtqueue *vq,
void *data,
gfp_t gfp);
+/* A desc with this init id is treated as an invalid desc */
+#define VIRTQUEUE_DESC_ID_INIT UINT_MAX
+int virtqueue_add_chain_desc(struct virtqueue *_vq,
+ uint64_t addr,
+ uint32_t len,
+ unsigned int *head_id,
+ unsigned int *prev_id,
+ bool in);
+
+int virtqueue_add_chain(struct virtqueue *_vq,
+ unsigned int head,
+ bool indirect,
+ struct vring_desc *indirect_desc,
+ void *data,
+ void *ctx);
+
bool virtqueue_kick(struct virtqueue *vq);
+bool virtqueue_kick_sync(struct virtqueue *vq);
+
+bool virtqueue_kick_async(struct virtqueue *vq, wait_queue_head_t wq);
+
bool virtqueue_kick_prepare(struct virtqueue *vq);
bool virtqueue_notify(struct virtqueue *vq);
I don't much care for this API. It does exactly what balloon needs,
but at cost of e.g. transparently busy-waiting. Unlikely to be
a good fit for anything else.
If you were referring to this API - virtqueue_add_chain_desc():
Busy waiting only happens when the vq is full (i.e. no desc left). If
necessary, I think we can add an input parameter like
"bool busywaiting", then the caller can decide to simply get a -ENOSPC
or busy wait to add when no desc is available.
If you don't like my original _first/_next/_last, you will
need to come up with something else.
I thought the above virtqueue_add_chain_des() performs the same
functionality as _first/next/last, which are used to grab descs from the
vq and chain them together. If not, could you please elaborate the
usage of the original proposal?
Best,
Wei
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