From: "Michael S. Tsirkin" <mst@redhat.com>
To: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: "David S. Miller" <davem@davemloft.net>,
Tiwei Bie <tiwei.bie@intel.com>,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH v4 2/2] virtio_ring: check desc == NULL when using indirect with packed
Date: Wed, 20 Oct 2021 04:24:33 -0400 [thread overview]
Message-ID: <20211020042350-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <1634696386.1682892-1-xuanzhuo@linux.alibaba.com>
On Wed, Oct 20, 2021 at 10:19:46AM +0800, Xuan Zhuo wrote:
> On Tue, 19 Oct 2021 09:21:51 -0400, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Tue, Oct 19, 2021 at 07:52:35PM +0800, Xuan Zhuo wrote:
> > > When using indirect with packed, we don't check for allocation failures.
> > > This patch checks that and fall back on direct.
> > >
> > > Fixes: 1ce9e6055fa ("virtio_ring: introduce packed ring support")
> > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > > ---
> > > drivers/virtio/virtio_ring.c | 13 ++++++++++---
> > > 1 file changed, 10 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > > index 91a46c4da87d..44a03b6e4dc4 100644
> > > --- a/drivers/virtio/virtio_ring.c
> > > +++ b/drivers/virtio/virtio_ring.c
> > > @@ -1065,6 +1065,9 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
> > >
> > > head = vq->packed.next_avail_idx;
> > > desc = alloc_indirect_packed(total_sg, gfp);
> > > + if (!desc)
> > > + /* fall back on direct */
> >
> > this comment belongs in virtqueue_add_packed right after
> > return.
> >
> > > + return -EAGAIN;
> > >
> >
> > -ENOMEM surely?
>
> virtqueue_add_indirect_packed() will return -ENOMEM when dma mmap fails, so we
> have to choose a different error code.
>
> Thanks.
That's exactly the point. Why would we want to recover from allocation
failure but not DMA map failure?
> >
> > > if (unlikely(vq->vq.num_free < 1)) {
> > > pr_debug("Can't add buf len 1 - avail = 0\n");
> > > @@ -1176,6 +1179,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
> > > unsigned int i, n, c, descs_used, err_idx;
> > > __le16 head_flags, flags;
> > > u16 head, id, prev, curr, avail_used_flags;
> > > + int err;
> > >
> > > START_USE(vq);
> > >
> > > @@ -1191,9 +1195,12 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
> > >
> > > BUG_ON(total_sg == 0);
> > >
> > > - if (virtqueue_use_indirect(_vq, total_sg))
> > > - return virtqueue_add_indirect_packed(vq, sgs, total_sg,
> > > - out_sgs, in_sgs, data, gfp);
> > > + if (virtqueue_use_indirect(_vq, total_sg)) {
> > > + err = virtqueue_add_indirect_packed(vq, sgs, total_sg, out_sgs,
> > > + in_sgs, data, gfp);
> > > + if (err != -EAGAIN)
> > > + return err;
> > > + }
> > >
> > > head = vq->packed.next_avail_idx;
> > > avail_used_flags = vq->packed.avail_used_flags;
> > > --
> > > 2.31.0
> >
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next prev parent reply other threads:[~2021-10-20 8:24 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-19 11:52 [PATCH v4 0/2] virtio_ring: check desc == NULL when packed and indirect Xuan Zhuo
2021-10-19 11:52 ` [PATCH v4 1/2] virtio_ring: fix style of virtqueue_add_indirect_packed Xuan Zhuo
2021-10-19 13:22 ` Michael S. Tsirkin
2021-10-19 11:52 ` [PATCH v4 2/2] virtio_ring: check desc == NULL when using indirect with packed Xuan Zhuo
2021-10-19 13:21 ` Michael S. Tsirkin
2021-10-20 2:19 ` Xuan Zhuo
2021-10-20 8:24 ` Michael S. Tsirkin [this message]
2021-10-20 11:07 ` Xuan Zhuo
2021-10-20 14:52 ` Michael S. Tsirkin
2021-10-21 1:54 ` Xuan Zhuo
2021-10-19 13:24 ` Michael S. Tsirkin
2021-10-19 13:23 ` [PATCH v4 0/2] virtio_ring: check desc == NULL when packed and indirect Michael S. Tsirkin
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