From: "Michael S. Tsirkin" <mst@redhat.com>
To: Eugenio Perez Martin <eperezma@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm list <kvm@vger.kernel.org>,
virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, Jason Wang <jasowang@redhat.com>
Subject: Re: [PATCH RFC v7 03/14] vhost: use batched get_vq_desc version
Date: Wed, 10 Jun 2020 11:13:36 -0400 [thread overview]
Message-ID: <20200610111147-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CAJaqyWdGKh5gSTndGuVPyJSgt3jfjfW4xNCrJ2tQ9f+mD8=sMQ@mail.gmail.com>
On Wed, Jun 10, 2020 at 02:37:50PM +0200, Eugenio Perez Martin wrote:
> > +/* This function returns a value > 0 if a descriptor was found, or 0 if none were found.
> > + * A negative code is returned on error. */
> > +static int fetch_descs(struct vhost_virtqueue *vq)
> > +{
> > + int ret;
> > +
> > + if (unlikely(vq->first_desc >= vq->ndescs)) {
> > + vq->first_desc = 0;
> > + vq->ndescs = 0;
> > + }
> > +
> > + if (vq->ndescs)
> > + return 1;
> > +
> > + for (ret = 1;
> > + ret > 0 && vq->ndescs <= vhost_vq_num_batch_descs(vq);
> > + ret = fetch_buf(vq))
> > + ;
>
> (Expanding comment in V6):
>
> We get an infinite loop this way:
> * vq->ndescs == 0, so we call fetch_buf() here
> * fetch_buf gets less than vhost_vq_num_batch_descs(vq); descriptors. ret = 1
> * This loop calls again fetch_buf, but vq->ndescs > 0 (and avail_vq ==
> last_avail_vq), so it just return 1
That's what
[PATCH RFC v7 08/14] fixup! vhost: use batched get_vq_desc version
is supposed to fix.
--
MST
next prev parent reply other threads:[~2020-06-10 15:13 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-10 11:35 [PATCH RFC v7 00/14] vhost: ring format independence Michael S. Tsirkin
2020-06-10 11:35 ` [PATCH RFC v7 01/14] vhost: option to fetch descriptors through an independent struct Michael S. Tsirkin
2020-06-10 11:35 ` [PATCH RFC v7 02/14] fixup! " Michael S. Tsirkin
2020-06-10 14:00 ` Eugenio Pérez
2020-06-10 11:36 ` [PATCH RFC v7 03/14] vhost: use batched get_vq_desc version Michael S. Tsirkin
2020-06-10 12:37 ` Eugenio Perez Martin
2020-06-10 15:13 ` Michael S. Tsirkin [this message]
2020-06-10 16:18 ` Eugenio Perez Martin
2020-06-11 11:30 ` Michael S. Tsirkin
2020-06-15 16:05 ` Eugenio Pérez
2020-06-16 15:23 ` Eugenio Perez Martin
2020-06-16 22:08 ` Michael S. Tsirkin
2020-06-10 14:29 ` Eugenio Pérez
2020-06-10 15:08 ` Michael S. Tsirkin
2020-06-10 15:12 ` Eugenio Perez Martin
2020-06-10 11:36 ` [PATCH RFC v7 04/14] vhost/net: pass net specific struct pointer Michael S. Tsirkin
2020-06-10 15:13 ` Eugenio Pérez
2020-06-10 11:36 ` [PATCH RFC v7 05/14] vhost: reorder functions Michael S. Tsirkin
2020-06-10 11:36 ` [PATCH RFC v7 06/14] vhost: format-independent API for used buffers Michael S. Tsirkin
2020-06-10 11:36 ` [PATCH RFC v7 07/14] fixup! " Michael S. Tsirkin
2020-06-10 11:36 ` [PATCH RFC v7 08/14] fixup! vhost: use batched get_vq_desc version Michael S. Tsirkin
2020-06-10 11:36 ` [PATCH RFC v7 09/14] vhost/net: convert to new API: heads->bufs Michael S. Tsirkin
2020-06-10 11:36 ` [PATCH RFC v7 10/14] vhost/net: avoid iov length math Michael S. Tsirkin
2020-06-10 11:36 ` [PATCH RFC v7 11/14] vhost/test: convert to the buf API Michael S. Tsirkin
2020-06-10 11:36 ` [PATCH RFC v7 12/14] vhost/scsi: switch to buf APIs Michael S. Tsirkin
2020-06-10 11:36 ` [PATCH RFC v7 13/14] vhost/vsock: switch to the buf API Michael S. Tsirkin
2020-06-10 11:36 ` [PATCH RFC v7 14/14] vhost: drop head based APIs Michael S. Tsirkin
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