linux-kernel - Re: [PATCH] scsi: virtio-scsi: Fix address translation failure of HighMem pages used by sg list

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Message-ID: <20120725100539.GB10075@stefanha-thinkpad.localdomain>
Date:	Wed, 25 Jul 2012 11:05:39 +0100
From:	Stefan Hajnoczi <stefanha@...ux.vnet.ibm.com>
To:	Wang Sen <senwang@...ux.vnet.ibm.com>
Cc:	linux-scsi@...r.kernel.org, JBottomley@...allels.com,
	pbonzini@...hat.com, mc@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: virtio-scsi: Fix address translation failure of
 HighMem pages used by sg list

On Wed, Jul 25, 2012 at 04:00:19PM +0800, Wang Sen wrote:
> When using the commands below to write some data to a virtio-scsi LUN of the 
> QEMU guest(32-bit) with 1G physical memory(qemu -m 1024), the qemu will crash.
> 
> 	# sudo mkfs.ext4 /dev/sdb  (/dev/sdb is the virtio-scsi LUN.)
> 	# sudo mount /dev/sdb /mnt
> 	# dd if=/dev/zero of=/mnt/file bs=1M count=1024
> 
> In current implementation, sg_set_buf is called to add buffers to sg list which
> is put into the virtqueue eventually. But there are some HighMem pages in 
> table->sgl can not get virtual address by sg_virt. So, sg_virt(sg_elem) may
> return NULL value. This will cause QEMU exit when virtqueue_map_sg is called 
> in QEMU because an invalid GPA is passed by virtqueue.
> 
> My solution is using sg_set_page instead of sg_set_buf.
> 
> I have tested the patch on my workstation. QEMU would not crash any more.
> 
> Signed-off-by: Wang Sen <senwang@...ux.vnet.ibm.com>
> ---
>  drivers/scsi/virtio_scsi.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Reviewed-by: Stefan Hajnoczi <stefanha@...ux.vnet.ibm.com>

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