From: Paolo Bonzini <pbonzini@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>,
"Richard W.M. Jones" <rjones@redhat.com>
Cc: jejb@linux.vnet.ibm.com, martin.petersen@oracle.com,
jasowang@redhat.com, linux-scsi@vger.kernel.org,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, hch@lst.de
Subject: Re: [PATCH 1/2] virtio: Reduce BUG if total_sg > virtqueue size to WARN.
Date: Fri, 11 Aug 2017 16:09:26 +0200 [thread overview]
Message-ID: <64d3c483-076b-1362-b284-30dda704f80c@redhat.com> (raw)
In-Reply-To: <20170811003621-mutt-send-email-mst@kernel.org>
On 10/08/2017 23:41, Michael S. Tsirkin wrote:
>>> Then we probably should fail probe if vq size is too small.
>> What does this mean?
>
> We must prevent driver from submitting s/g lists > vq size to device.
What is the rationale for the limit? It makes no sense if indirect
descriptors are available, especially because...
> Either tell linux to avoid s/g lists that are too long, or
> simply fail request if this happens, or refuse to attach driver to device.
>
> Later option would look something like this within probe:
>
> for (i = VIRTIO_SCSI_VQ_BASE; i < num_vqs; i++)
> if (vqs[i]->num < MAX_SG_USED_BY_LINUX)
> goto err;
>
>
> I don't know what's MAX_SG_USED_BY_LINUX though.
>
... both virtio-blk and virtio-scsi transmit their own value for the
maximum sg list size (max_seg in virtio-scsi, seg_max in virtio-blk).
Paolo
next prev parent reply other threads:[~2017-08-11 14:09 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-10 16:40 [PATCH 0/2] virtio_scsi: Set can_queue based on size of virtqueue Richard W.M. Jones
2017-08-10 16:40 ` [PATCH 1/2] virtio: Reduce BUG if total_sg > virtqueue size to WARN Richard W.M. Jones
2017-08-10 16:47 ` Paolo Bonzini
2017-08-10 21:21 ` Michael S. Tsirkin
2017-08-10 21:30 ` Richard W.M. Jones
2017-08-10 21:31 ` Michael S. Tsirkin
2017-08-10 21:35 ` Richard W.M. Jones
2017-08-10 21:41 ` Michael S. Tsirkin
2017-08-10 21:50 ` Richard W.M. Jones
2017-08-11 14:09 ` Paolo Bonzini [this message]
2017-08-11 17:23 ` Michael S. Tsirkin
2017-08-11 18:36 ` Paolo Bonzini
2017-08-10 16:40 ` [PATCH 2/2] virtio: virtio_scsi: Set can_queue to the length of the virtqueue Richard W.M. Jones
2017-08-10 16:46 ` Paolo Bonzini
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