On Thu, 12 Oct 2023 05:15:52 -0400, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote:
> On Wed, Oct 11, 2023 at 05:27:07PM +0800, Xuan Zhuo wrote:
> > virtqueue_set_dma_premapped() adds a new parameter to disable the
> > virtqueue premapped mode.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> > ---
> > drivers/net/virtio_net.c | 2 +-
> > drivers/virtio/virtio_ring.c | 11 ++++++++---
> > include/linux/virtio.h | 2 +-
> > 3 files changed, 10 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index fe7f314d65c9..6b5f47ebf9b2 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -737,7 +737,7 @@ static void virtnet_rq_set_premapped(struct virtnet_info *vi)
> > return;
> >
> > for (i = 0; i < vi->max_queue_pairs; i++) {
> > - if (virtqueue_set_dma_premapped(vi->rq[i].vq))
> > + if (virtqueue_set_dma_premapped(vi->rq[i].vq, true))
> > continue;
> >
> > vi->rq[i].do_dma = true;
> > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > index 51d8f3299c10..b3ded56722f4 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -2784,7 +2784,7 @@ EXPORT_SYMBOL_GPL(virtqueue_resize);
> > * 0: success.
> > * -EINVAL: vring does not use the dma api, so we can not enable premapped mode.
> > */
> > -int virtqueue_set_dma_premapped(struct virtqueue *_vq)
> > +int virtqueue_set_dma_premapped(struct virtqueue *_vq, bool mode)
> > {
> > struct vring_virtqueue *vq = to_vvq(_vq);
> > u32 num;
> > @@ -2803,8 +2803,13 @@ int virtqueue_set_dma_premapped(struct virtqueue *_vq)
> > return -EINVAL;
> > }
> >
> > - vq->premapped = true;
> > - vq->do_unmap = false;
> > + if (mode) {
> > + vq->premapped = true;
> > + vq->do_unmap = false;
> > + } else {
> > + vq->premapped = false;
> > + vq->do_unmap = vq->use_dma_api;
> > + }
> >
> > END_USE(vq);
> >
> > diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> > index 4cc614a38376..1cf7b004348b 100644
> > --- a/include/linux/virtio.h
> > +++ b/include/linux/virtio.h
> > @@ -81,7 +81,7 @@ bool virtqueue_enable_cb(struct virtqueue *vq);
> >
> > unsigned virtqueue_enable_cb_prepare(struct virtqueue *vq);
> >
> > -int virtqueue_set_dma_premapped(struct virtqueue *_vq);
> > +int virtqueue_set_dma_premapped(struct virtqueue *_vq, bool mode);
> >
> > bool virtqueue_poll(struct virtqueue *vq, unsigned);
>
> Wait a sec I thought we never change premapped. If you make this
> dynamic don't you need a bunch of locking?
> Or maybe queue is empty when you change this?
> If yes pls add a bunch of BUG_ON checks to make sure this is not misused.
Actually, this api is called immediately after the vq init or vq reset.
We already have such a check.
Thanks.
/**
* virtqueue_set_dma_premapped - set the vring premapped mode
* @_vq: the struct virtqueue we're talking about.
*
* Enable the premapped mode of the vq.
*
* The vring in premapped mode does not do dma internally, so the driver must
* do dma mapping in advance. The driver must pass the dma_address through
* dma_address of scatterlist. When the driver got a used buffer from
* the vring, it has to unmap the dma address.
*
* This function must be called immediately after creating the vq, or after vq
* reset, and before adding any buffers to it.
*
* Caller must ensure we don't call this with other virtqueue operations
* at the same time (except where noted).
*
* Returns zero or a negative error.
* 0: success.
* -EINVAL: vring does not use the dma api, so we can not enable premapped mode.
*/
int virtqueue_set_dma_premapped(struct virtqueue *_vq, bool mode)
{
struct vring_virtqueue *vq = to_vvq(_vq);
u32 num;
START_USE(vq);
num = vq->packed_ring ? vq->packed.vring.num : vq->split.vring.num;
--> if (num != vq->vq.num_free) {
END_USE(vq);
return -EINVAL;
}
if (!vq->use_dma_api) {
END_USE(vq);
return -EINVAL;
}
if (mode) {
vq->premapped = true;
vq->do_unmap = false;
} else {
vq->premapped = false;
vq->do_unmap = vq->use_dma_api;
}
END_USE(vq);
return 0;
}
EXPORT_SYMBOL_GPL(virtqueue_set_dma_premapped);
>
>
> > --
> > 2.32.0.3.g01195cf9f
>
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