From: Jason Wang <jasowang@redhat.com>
To: Connor Kuehl <ckuehl@redhat.com>, virtio-fs@redhat.com
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, stefanha@redhat.com,
vgoyal@redhat.com, miklos@szeredi.hu, mst@redhat.com
Subject: Re: [PATCH 1/3] virtio_ring: always warn when descriptor chain exceeds queue size
Date: Mon, 22 Mar 2021 11:22:15 +0800 [thread overview]
Message-ID: <fa4988fa-a671-0abf-f922-6b362faf10d5@redhat.com> (raw)
In-Reply-To: <20210318135223.1342795-2-ckuehl@redhat.com>
在 2021/3/18 下午9:52, Connor Kuehl 写道:
> From section 2.6.5.3.1 (Driver Requirements: Indirect Descriptors)
> of the virtio spec:
>
> "A driver MUST NOT create a descriptor chain longer than the Queue
> Size of the device."
>
> This text suggests that the warning should trigger even if
> indirect descriptors are in use.
So I think at least the commit log needs some tweak.
For split virtqueue. We had:
2.6.5.2 Driver Requirements: The Virtqueue Descriptor Table
Drivers MUST NOT add a descriptor chain longer than 2^32 bytes in total;
this implies that loops in the descriptor chain are forbidden!
2.6.5.3.1 Driver Requirements: Indirect Descriptors
A driver MUST NOT create a descriptor chain longer than the Queue Size
of the device.
If I understand the spec correctly, the check is only needed for a
single indirect descriptor table?
For packed virtqueue. We had:
2.7.17 Driver Requirements: Scatter-Gather Support
A driver MUST NOT create a descriptor list longer than allowed by the
device.
A driver MUST NOT create a descriptor list longer than the Queue Size.
2.7.19 Driver Requirements: Indirect Descriptors
A driver MUST NOT create a descriptor chain longer than allowed by the
device.
So it looks to me the packed part is fine.
Note that if I understand the spec correctly 2.7.17 implies 2.7.19.
Thanks
>
> Reported-by: Stefan Hajnoczi <stefanha@redhat.com>
> Signed-off-by: Connor Kuehl <ckuehl@redhat.com>
> ---
> drivers/virtio/virtio_ring.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 71e16b53e9c1..1bc290f9ba13 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -444,11 +444,12 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
>
> head = vq->free_head;
>
> + WARN_ON_ONCE(total_sg > vq->split.vring.num);
> +
> if (virtqueue_use_indirect(_vq, total_sg))
> desc = alloc_indirect_split(_vq, total_sg, gfp);
> else {
> desc = NULL;
> - WARN_ON_ONCE(total_sg > vq->split.vring.num && !vq->indirect);
> }
>
> if (desc) {
> @@ -1118,6 +1119,8 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
>
> BUG_ON(total_sg == 0);
>
> + WARN_ON_ONCE(total_sg > vq->packed.vring.num);
> +
> if (virtqueue_use_indirect(_vq, total_sg))
> return virtqueue_add_indirect_packed(vq, sgs, total_sg,
> out_sgs, in_sgs, data, gfp);
> @@ -1125,8 +1128,6 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
> head = vq->packed.next_avail_idx;
> avail_used_flags = vq->packed.avail_used_flags;
>
> - WARN_ON_ONCE(total_sg > vq->packed.vring.num && !vq->indirect);
> -
> desc = vq->packed.vring.desc;
> i = head;
> descs_used = total_sg;
next prev parent reply other threads:[~2021-03-22 3:23 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-18 13:52 [PATCH 0/3] virtiofs: split requests that exceed virtqueue size Connor Kuehl
2021-03-18 13:52 ` [PATCH 1/3] virtio_ring: always warn when descriptor chain exceeds queue size Connor Kuehl
2021-03-22 3:22 ` Jason Wang [this message]
2021-03-22 8:17 ` Michael S. Tsirkin
2021-03-23 2:38 ` Jason Wang
2021-03-18 13:52 ` [PATCH 2/3] virtiofs: split requests that exceed virtqueue size Connor Kuehl
2021-03-18 15:17 ` Miklos Szeredi
2021-03-18 15:52 ` Connor Kuehl
2021-03-20 20:04 ` Michael S. Tsirkin
2021-03-22 19:01 ` Vivek Goyal
2021-03-24 15:09 ` Connor Kuehl
2021-03-24 15:30 ` Miklos Szeredi
2021-03-24 15:31 ` Connor Kuehl
2021-03-19 13:49 ` Vivek Goyal
2021-03-19 14:16 ` Connor Kuehl
2021-03-22 15:47 ` Stefan Hajnoczi
2021-03-18 13:52 ` [PATCH 3/3] fuse: fix typo for fuse_conn.max_pages comment Connor Kuehl
2021-03-22 3:42 ` Jason Wang
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