Re: Errors on MMIO read access on VM suspend / resume operations

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2011-01-18 04:03, Stefan Berger wrote:
> On 01/16/2011 09:43 AM, Avi Kivity wrote:
>> On 01/14/2011 09:27 PM, Stefan Berger wrote:
>>>
>>>>
>>>> Can you sprinkle some printfs() arount kvm_run (in qemu-kvm.c) to
>>>> verify this?
>>>>
>>> Here's what I did:
>>>
>>>
>>> interrupt exit requested
>>
>> It appears from this you're using qemu.git.  Please try qemu-kvm.git,
>> where the code appears to be correct.
>>
> Cc'ing qemu-devel now. For reference, here the initial problem description:
> 
> http://www.spinics.net/lists/kvm/msg48274.html
> 
> I didn't know there was another tree...
> 
> I have seen now a couple of suspends-while-reading with patches applied
> to the qemu-kvm.git tree and indeed, when run with the same host kernel
> and VM I do not see the debugging dumps due to double-reads that I would
> have anticipated seeing by now. Now what? Can this be easily fixed in
> the other Qemu tree as well?

Please give this a try:

git://git.kiszka.org/qemu-kvm.git queues/kvm-upstream

I bet (& hope) "kvm: Unconditionally reenter kernel after IO exits"
fixes the issue for you. If other problems pop up with that tree, also
try resetting to that particular commit.

I'm currently trying to shake all those hidden or forgotten bug fixes
out of qemu-kvm and port them upstream. Most of those subtle differences
should hopefully soon be history.

> 
> One thing I'd like to mention is that I have seen what I think are
> interrupt stalls when running my tests inside the qemu-kvm.git tree
> version and not suspending at all. A some point the interrupt counter in
> the guest kernel does not increase anymore even though I see the device
> model raising the IRQ and lowering it. The same tests run literally
> forever in the qemu.git tree version of Qemu.

What about qemu-kmv and -no-kvm-irqchip?

Jan

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