Re: [REGRESSION] 07ec51480b5e ("virtio_pci: use shared interrupts for virtqueues") causes crashes in guest

[Christoph Hellwig <hch@lst.de>]

On Thu, Mar 23, 2017 at 01:13:50PM +0800, Jason Wang wrote:
>
>
> On 2017年03月23日 08:30, Laura Abbott wrote:
>> Hi,
>>
>> Fedora has received multiple reports of crashes when running
>> 4.11 as a guest
>>
>> https://bugzilla.redhat.com/show_bug.cgi?id=1430297
>> https://bugzilla.redhat.com/show_bug.cgi?id=1434462
>> https://bugzilla.kernel.org/show_bug.cgi?id=194911
>> https://bugzilla.redhat.com/show_bug.cgi?id=1433899
>>
>> The crashes are not always consistent but they are generally
>> some flavor of oops or GPF in virtio related code. Multiple people
>> have done bisections (Thank you Thorsten Leemhuis and
>> Richard W.M. Jones) and found this commit to be at fault
>>
>> 07ec51480b5eb1233f8c1b0f5d7a7c8d1247c507 is the first bad commit
>> commit 07ec51480b5eb1233f8c1b0f5d7a7c8d1247c507
>> Author: Christoph Hellwig <hch@lst.de>
>> Date:   Sun Feb 5 18:15:19 2017 +0100
>>
>>      virtio_pci: use shared interrupts for virtqueues
>>           This lets IRQ layer handle dispatching IRQs to separate handlers 
>> for the
>>      case where we don't have per-VQ MSI-X vectors, and allows us to greatly
>>      simplify the code based on the assumption that we always have interrupt
>>      vector 0 (legacy INTx or config interrupt for MSI-X) available, and
>>      any other interrupt is request/freed throught the VQ, even if the
>>      actual interrupt line might be shared in some cases.
>>           This allows removing a great deal of variables keeping track of 
>> the
>>      interrupt state in struct virtio_pci_device, as we can now simply walk the
>>      list of VQs and deal with per-VQ interrupt handlers there, and only treat
>>      vector 0 special.
>>           Additionally clean up the VQ allocation code to properly unwind 
>> on error
>>      instead of having a single global cleanup label, which is error prone,
>>      and in this case also leads to more code.
>>           Signed-off-by: Christoph Hellwig <hch@lst.de>
>>      Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>>
>> :040000 040000 79a8267ffb73f9d244267c5f68365305bddd4696 8832a160b978710bbd24ba6966f462b3faa27fcc M	drivers
>>
>> It doesn't revert cleanly so we haven't been able to do a clean
>> test. Any ideas?
>>
>> Thanks,
>> Laura
>
> Hello:
>
> Can you try the attached patch to see if it solves the problem? (At least 
> it silent KASan warnings for me).

This looks like a correct fix to me, independent of fixing the original
bug or not:

Reviewed-by: Christoph Hellwig <hch@lst.de>