From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>,
virtualization@lists.linux-foundation.org,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Jesper Dangaard Brouer <hawk@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH vhost v10 02/10] virtio_ring: introduce virtqueue_set_premapped()
Date: Wed, 28 Jun 2023 09:34:21 +0800 [thread overview]
Message-ID: <1687916061.7751381-1-xuanzhuo@linux.alibaba.com> (raw)
In-Reply-To: <20230627105503-mutt-send-email-mst@kernel.org>
On Tue, 27 Jun 2023 10:56:54 -0400, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> On Tue, Jun 27, 2023 at 04:50:01PM +0800, Xuan Zhuo wrote:
> > On Tue, 27 Jun 2023 16:03:23 +0800, Jason Wang <jasowang@redhat.com> wrote:
> > > On Fri, Jun 2, 2023 at 5:22 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
> > > >
> > > > This helper allows the driver change the dma mode to premapped mode.
> > > > Under the premapped mode, the virtio core do not do dma mapping
> > > > internally.
> > > >
> > > > This just work when the use_dma_api is true. If the use_dma_api is false,
> > > > the dma options is not through the DMA APIs, that is not the standard
> > > > way of the linux kernel.
> > > >
> > > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > > > ---
> > > > drivers/virtio/virtio_ring.c | 40 ++++++++++++++++++++++++++++++++++++
> > > > include/linux/virtio.h | 2 ++
> > > > 2 files changed, 42 insertions(+)
> > > >
> > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > > > index 72ed07a604d4..2afdfb9e3e30 100644
> > > > --- a/drivers/virtio/virtio_ring.c
> > > > +++ b/drivers/virtio/virtio_ring.c
> > > > @@ -172,6 +172,9 @@ struct vring_virtqueue {
> > > > /* Host publishes avail event idx */
> > > > bool event;
> > > >
> > > > + /* Do DMA mapping by driver */
> > > > + bool premapped;
> > > > +
> > > > /* Head of free buffer list. */
> > > > unsigned int free_head;
> > > > /* Number we've added since last sync. */
> > > > @@ -2059,6 +2062,7 @@ static struct virtqueue *vring_create_virtqueue_packed(
> > > > vq->packed_ring = true;
> > > > vq->dma_dev = dma_dev;
> > > > vq->use_dma_api = vring_use_dma_api(vdev);
> > > > + vq->premapped = false;
> > > >
> > > > vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) &&
> > > > !context;
> > > > @@ -2548,6 +2552,7 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index,
> > > > #endif
> > > > vq->dma_dev = dma_dev;
> > > > vq->use_dma_api = vring_use_dma_api(vdev);
> > > > + vq->premapped = false;
> > > >
> > > > vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) &&
> > > > !context;
> > > > @@ -2691,6 +2696,41 @@ int virtqueue_resize(struct virtqueue *_vq, u32 num,
> > > > }
> > > > EXPORT_SYMBOL_GPL(virtqueue_resize);
> > > >
> > > > +/**
> > > > + * virtqueue_set_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. So the driver must call
> > > > + * virtqueue_get_buf_premapped()/virtqueue_detach_unused_buf_premapped().
> > > > + *
> > > > + * This must be called before adding any buf to vring.
> > >
> > > And any old buffer should be detached?
> >
> > I mean that before adding any buf, So there are not old buffer.
> >
>
> Oh. So put this in the same sentence:
>
> This function must be called immediately after creating the vq,
> or after vq reset, and before adding any buffers to it.
OK, thanks.
>
>
> > >
> > > > + * So this should be called immediately after init vq or vq reset.
>
> Do you really need to call this again after each reset?
YES
Thanks.
>
>
> > > Any way to detect and warn in this case? (not a must if it's too
> > > expensive to do the check)
> >
> >
> > I can try to check whether the qeueu is empty.
> >
> >
> > >
> > > > + *
> > > > + * 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_premapped(struct virtqueue *_vq)
> > > > +{
> > > > + struct vring_virtqueue *vq = to_vvq(_vq);
> > > > +
> > > > + if (!vq->use_dma_api)
> > > > + return -EINVAL;
> > > > +
> > > > + vq->premapped = true;
> > >
> > > I guess there should be a way to disable it. Would it be useful for
> > > the case when AF_XDP sockets were destroyed?
> >
> > Yes.
> >
> > When we reset the queue, the vq->premapped will be set to 0.
> >
> > The is called after find_vqs or reset vq.
> >
> > Thanks.
> >
> >
> >
> > >
> > > Thanks
> > >
> > >
> > > > +
> > > > + return 0;
> > > > +}
> > > > +EXPORT_SYMBOL_GPL(virtqueue_set_premapped);
> > > > +
> > > > /* Only available for split ring */
> > > > struct virtqueue *vring_new_virtqueue(unsigned int index,
> > > > unsigned int num,
> > > > diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> > > > index b93238db94e3..1fc0e1023bd4 100644
> > > > --- a/include/linux/virtio.h
> > > > +++ b/include/linux/virtio.h
> > > > @@ -78,6 +78,8 @@ bool virtqueue_enable_cb(struct virtqueue *vq);
> > > >
> > > > unsigned virtqueue_enable_cb_prepare(struct virtqueue *vq);
> > > >
> > > > +int virtqueue_set_premapped(struct virtqueue *_vq);
> > > > +
> > > > bool virtqueue_poll(struct virtqueue *vq, unsigned);
> > > >
> > > > bool virtqueue_enable_cb_delayed(struct virtqueue *vq);
> > > > --
> > > > 2.32.0.3.g01195cf9f
> > > >
> > >
>
next prev parent reply other threads:[~2023-06-28 1:34 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-02 9:21 [PATCH vhost v10 00/10] virtio core prepares for AF_XDP Xuan Zhuo
2023-06-02 9:21 ` [PATCH vhost v10 01/10] virtio_ring: put mapping error check in vring_map_one_sg Xuan Zhuo
2023-06-27 8:03 ` Jason Wang
2023-06-02 9:21 ` [PATCH vhost v10 02/10] virtio_ring: introduce virtqueue_set_premapped() Xuan Zhuo
2023-06-27 8:03 ` Jason Wang
2023-06-27 8:50 ` Xuan Zhuo
2023-06-27 14:56 ` Michael S. Tsirkin
2023-06-28 1:34 ` Xuan Zhuo [this message]
2023-06-02 9:21 ` [PATCH vhost v10 03/10] virtio_ring: split: support add premapped buf Xuan Zhuo
2023-06-27 8:03 ` Jason Wang
2023-06-27 9:01 ` Xuan Zhuo
2023-06-02 9:22 ` [PATCH vhost v10 04/10] virtio_ring: packed: " Xuan Zhuo
2023-06-27 8:03 ` Jason Wang
2023-06-27 9:05 ` Xuan Zhuo
2023-06-02 9:22 ` [PATCH vhost v10 05/10] virtio_ring: split-detach: support return dma info to driver Xuan Zhuo
2023-06-22 19:36 ` Michael S. Tsirkin
2023-06-25 2:10 ` Xuan Zhuo
2023-06-27 8:03 ` Jason Wang
2023-06-27 9:21 ` Xuan Zhuo
2023-06-02 9:22 ` [PATCH vhost v10 06/10] virtio_ring: packed-detach: " Xuan Zhuo
2023-06-02 11:40 ` Michael S. Tsirkin
2023-06-02 9:22 ` [PATCH vhost v10 07/10] virtio_ring: introduce helpers for premapped Xuan Zhuo
2023-06-04 13:45 ` Michael S. Tsirkin
2023-06-05 2:06 ` Xuan Zhuo
2023-06-05 5:38 ` Michael S. Tsirkin
2023-06-06 2:01 ` Xuan Zhuo
2023-06-22 19:29 ` Michael S. Tsirkin
2023-06-02 9:22 ` [PATCH vhost v10 08/10] virtio_ring: introduce virtqueue_dma_dev() Xuan Zhuo
2023-06-02 9:22 ` [PATCH vhost v10 09/10] virtio_ring: introduce virtqueue_add_sg() Xuan Zhuo
2023-06-02 9:22 ` [PATCH vhost v10 10/10] virtio_net: support dma premapped Xuan Zhuo
2023-06-03 6:31 ` Jakub Kicinski
2023-06-05 2:10 ` Xuan Zhuo
2023-06-05 5:44 ` Michael S. Tsirkin
2023-06-06 2:11 ` Xuan Zhuo
2023-06-22 12:15 ` Michael S. Tsirkin
2023-06-25 2:43 ` Xuan Zhuo
2023-06-27 8:03 ` Jason Wang
2023-06-27 9:23 ` Xuan Zhuo
2023-06-03 6:29 ` [PATCH vhost v10 00/10] virtio core prepares for AF_XDP Jakub Kicinski
2023-06-05 1:58 ` Xuan Zhuo
2023-06-07 14:05 ` Christoph Hellwig
2023-06-07 20:15 ` Michael S. Tsirkin
2023-06-21 6:42 ` Xuan Zhuo
2023-06-25 7:19 ` Jason Wang
2023-06-22 19:38 ` Michael S. Tsirkin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1687916061.7751381-1-xuanzhuo@linux.alibaba.com \
--to=xuanzhuo@linux.alibaba.com \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=davem@davemloft.net \
--cc=edumazet@google.com \
--cc=hawk@kernel.org \
--cc=jasowang@redhat.com \
--cc=john.fastabend@gmail.com \
--cc=kuba@kernel.org \
--cc=mst@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.com \
--cc=virtualization@lists.linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).