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Date: Mon, 15 Nov 2010 15:16:32 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] virtio-blk broken after system reset
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To: Jan Kiszka <jan.kiszka@web.de>
Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, Gleb Natapov <gleb@redhat.com>, Stefan Hajnoczi <stefanha@gmail.com>, Michael Tokarev <mjt@tls.msk.ru>, qemu-devel <qemu-devel@nongnu.org>, Kevin O'Connor <kevin@koconnor.net>

On 11/13/2010 04:09 AM, Jan Kiszka wrote:
>
> There is also real hw out there that goes into an error state if it's
> misprogrammed.
>
> I think we have to remove all those premature exits. They also prevent
> handing the device inside the guest to an untrusted driver (relevant
> once we have IOMMU emulation).
>    

I think the key to achieving this is to isolate the device within QEMU.

IOW, have all fd callbacks, bottom halves, etc. tagged with a device 
context.  Have a mechanism that raises an error on a device that can 
then be used to stop issuing any type of callback to the device until reset.

Obviously, we can fix some of these by just simple code refactoring.

Regards,

Anthony Liguori

>> Why it is trying to print things to stderr is a different
>> matter, it should be using a proper error-reporting routine,
>> but this is a different story.
>>      
> Jep. Even worse: the above message is not dumped to the console as the
> stream isn't flushed on exit.
>
> Jan
>
>