Re: guest suspend/resume & virtio: vring errors

[Michael Tokarev <mjt@tls.msk.ru>]

09.07.2011 13:55, Gleb Natapov wrote:
> On Sat, Jul 09, 2011 at 01:47:25PM +0400, Michael Tokarev wrote:
>> 09.07.2011 13:17, Gleb Natapov wrote:

>> This means that neither in-guest suspend/resume nor
>> qemu-kvm migrate-to-file (which fails for a different
>> reason I'm trying to debug now) works.  Which is very
>> unfortunate.
>>
> Migration to file should work, or, at least, is a different problem.
> It does not require guest cooperation.

Sure, that's why I said "different reason".  That's what
prompted me to try in-guest migration - because I weren't
able to use migrate-to-file, but I needed to replace the
qemu-kvm binary after a security fix.

>> It does not work with any version of windows I tried, too
>> (which is winXP, win7 32 and win7 64bits).  Windows enters
>> an endless loop with a black screen during suspend (eating
>> 100% CPU time).
>>
> Heh. Is this S4 or S3 suspend resume? Looks like recent breakage.
> The only knows problem to me is in win7/2008 S3 resume + net.

How can I know if it's S3 or S4?  And I can't say it's recent:
0.14.1 works (or actually does not work) exactly the same in
this respect as current git: suspend/resume is equally broken.

>> What's wrong/broken in linux?  Can it be fixed?
>>
> Complete lack of regression testing.

Hm.  You wrote:

> Yes, but Linux and suspend/resume are not best friends. Sometimes it
> works by mistake, but next merged patch fixes it and suspend/resume
> returns to its normal broken state.

So regression testing should detect and raise an alarm
when it works by mistake.  But can it be fixed to work
by design instead, after which regression testing gets
entrirely new meaning ? :)

Thanks,

/mjt