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Date: Mon, 09 May 2011 16:31:10 +0200
From: Alexander Graf <agraf@suse.de>
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Subject: Re: [Qemu-devel] ahci: crash after duplicate bh registration
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To: Kevin Wolf <kwolf@redhat.com>
Cc: Jan Kiszka <jan.kiszka@web.de>, qemu-devel <qemu-devel@nongnu.org>

On 05/09/2011 04:26 PM, Kevin Wolf wrote:
> Am 09.05.2011 16:12, schrieb Alexander Graf:
>> On 05/08/2011 09:10 PM, Jan Kiszka wrote:
>>> Hi Alex,
>>>
>>> I've seen crashes caused by ahci_check_cmd_bh unregistering a NULL bh.
>>> It looks like ahci_dma_set_inactive can a called while there is already
>>> a bh hanging around. Patch below cures the issue, but I have no clue if
>>> such an invocation order is valid at all.
>> It's certainly guest triggerable, so yes, let's check here.
>>
>> Acked-by: Alexander Graf<agraf@suse.de>
> Yes, the change makes sense to me. Please resend this as a proper patch,
> Jan.
>
> However, I still think Jan's question is valid: Is the AHCI emulation
> supposed to run multiple DMA requests at once using the core.c
> functions? I'd find it surprising if this actually worked well.

Not through the IDE core, no. There it can process a queue of IDE 
commands after each other or do NCQ, but that goes a different code 
patch, can do multiple requests at once though.

I'm not sure how this got triggered.


Alex