Re: [PATCH] scsi: virtio-scsi: Fix address translation failure ofHighMem pages used by sg list

[Sen Wang]

2012/7/25 Stefan Hajnoczi <stefanha@xxxxxxxxxxxxxxxxxx>:
> On Wed, Jul 25, 2012 at 10:44:14AM +0200, Paolo Bonzini wrote:
>> Il 25/07/2012 10:29, Wang Sen ha scritto:
>> > 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.
>>
>> Heh, I was compiling (almost) the same patch as we speak. :)
>>
>> I've never seen QEMU crash; the VM would more likely just fail to boot
>> with a panic.  But it's the same bug anyway.
>
> It's not a segfault "crash", I think it hits an abort(3) in QEMU's
> virtio code when trying to map an invalid guest physical address.

How the guest boot fail? I never met this case.

>
> Stefan
>
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-- 
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Wang Sen
Addr: XUPT,Xi'an,Shaanxi,China
Email: kelvin.xupt@xxxxxxxxx
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