Re: [Qemu-devel] Guest unresponsive after Virtqueue size exceeded error

[Fernando Casas Schössow]

Hi Ladi,

Small update. Memtest86+ was running on the host for more than 54 hours. 8 
passes were completed and no memory errors found. For now I think we can assume 
that the host memory is ok.

I just started all the guests one hour ago. I will monitor them and once one 
fails I will attach the debugger and let you know.

Thanks.

Fer

On jue, jun 22, 2017 at 9:43 , Ladi Prosek <address@hidden> wrote:
Hi Fernando, On Wed, Jun 21, 2017 at 2:19 PM, Fernando Casas Schössow 
<address@hidden<mailto:address@hidden>> wrote:
Hi Ladi, Sorry for the delay in my reply. I will leave the host kernel alone 
for now then. For the last 15 hours or so I'm running memtest86+ on the host. 
So far so good. Two passes no errors so far. I will try to leave it running for 
at least another 24hr and report back the results. Hopefully we can discard the 
memory issue at hardware level. Regarding KSM, that will be the next thing I 
will disable if after removing the balloon device guests still crash. About 
leaving a guest in a failed state for you to debug it remotely, that's 
absolutely an option. We just need to coordinate so I can give you remote 
access to the host and so on. Let me know if any preparation is needed in 
advance and which tools you need installed on the host.
I think that gdbserver attached to the QEMU process should be enough. When the 
VM gets into the broken state please do something like: gdbserver --attach 
host:12345 <QEMU pid> and let me know the host name and port (12345 in the 
above example).
Once I again I would like to thank you for all your help and your great 
disposition!
You're absolutely welcome, I don't think I've done anything helpful so far :)
Cheers, Fer On mar, jun 20, 2017 at 9:52 , Ladi Prosek 
<address@hidden<mailto:address@hidden>> wrote: The host kernel is less likely 
to be responsible for this, in my opinion. I'd hold off on that for now. And 
last but not least KSM is enabled on the host. Should I disable it? Could be 
worth the try. Following your advice I will run memtest on the host and report 
back. Just as a side comment, the host is running on ECC memory. I see. Would 
it be possible for you, once a guest is in the broken state, to make it 
available for debugging? By attaching gdb to the QEMU process for example and 
letting me poke around it remotely? Thanks!