Messages in this thread | | | Date | Wed, 12 Jul 2017 21:29:00 +0800 | From | Wei Wang <> | Subject | Re: [PATCH v12 5/8] virtio-balloon: VIRTIO_BALLOON_F_SG |
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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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