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Date: Sat, 18 Aug 2012 20:52:56 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [RFC-v2 6/6] virtio-scsi: Fix incorrect
 VirtIOSCSI->cmd_vqs[0] definition
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To: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, kvm-devel <kvm@vger.kernel.org>, "Michael S. Tsirkin" <mst@redhat.com>, Jan Kiszka <jan.kiszka@siemens.com>, qemu-devel <qemu-devel@nongnu.org>, lf-virt <virtualization@lists.linux-foundation.org>, Anthony Liguori <aliguori@linux.vnet.ibm.com>, target-devel <target-devel@vger.kernel.org>, Hannes Reinecke <hare@suse.de>, Zhi Yong Wu <wuzhy@cn.ibm.com>, Christoph Hellwig <hch@lst.de>

Il 14/08/2012 22:20, Nicholas A. Bellinger ha scritto:
>>> > > Since virtio_scsi currently assumes a single vqs for data, this patch
>>> > > simply changes ->cmd_vqs[1] to handle the single VirtQueue.

Wrong, multiqueue works just fine. :)  It's just the kernel driver that
doesn't support it yet.

>>> > > Cc: Paolo Bonzini <pbonzini@redhat.com>
>>> > > Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
>>> > > Cc: Michael S. Tsirkin <mst@redhat.com>
>>> > > Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
>> > 
>> > This is a bugfix we need even without vhost, right?
>> > 
> I believe so, as it appears to be stomping past the end of memory for
> every virtio-scsi initialization regardless of vhost usage.. 

You just did a wrong merge.  When commit d2ad7dd (virtio-scsi: add
multiqueue capability, 2012-04-06) changed cmd_vq from pointer to array
of pointers, you should have moved the following fields to the middle of
the struct, just like that commit did.

Paolo