Re: [win-pv-devel] Problems with xenvbd

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: RafaÅ WojdyÅa [mailto:omeg@xxxxxxxxxxxxxxxxxxxxxx]
> Sent: 20 August 2015 23:03
> To: Paul Durrant; win-pv-devel@xxxxxxxxxxxxxxxxxxxx
> Subject: Re: [win-pv-devel] Problems with xenvbd
> 
> On 2015-08-19 23:25, Paul Durrant wrote:
> >> -----Original Message----- From:
> >> win-pv-devel-bounces@xxxxxxxxxxxxxxxxxxxx [mailto:win-pv-devel-
> >> bounces@xxxxxxxxxxxxxxxxxxxx] On Behalf Of Rafal Wojdyla Sent: 18
> >> August 2015 14:33 To: win-pv-devel@xxxxxxxxxxxxxxxxxxxx Subject:
> >> [win-pv-devel] Problems with xenvbd
> >>
> >> Hi,
> >>
> >> I've been testing the current pvdrivers code in preparation for
> >> creating upstream patches for my xeniface additions and I noticed
> >> than xenvbd seems to be very unstable for me. I'm not sure if it's
> >> a problem with xenvbd itself or my code because it seemed to only
> >> manifest when the full suite of our guest tools was installed along
> >> with xenvbd. In short, most of the time the system crashed with
> >> kernel memory corruption in seemingly random processes shortly
> >> after start. Driver Verifier didn't seem to catch anything. You can
> >> see a log from one such crash in the attachment crash1.txt.
> >>
> >> Today I tried to perform some more tests but this time without our
> >> guest tools (only pvdrivers and our shared libraries were
> >> installed). To my surprise now Driver Verifier was crashing the
> >> system every time in xenvbd (see crash2.txt). I don't know why it
> >> didn't catch that previously... If adding some timeout to the
> >> offending wait doesn't break anything I'll try that to see if I can
> >> reproduce the previous memory corruptions.
> >>
> >
> > Those crashes do look odd. I'm on PTO for the next week but I'll have
> > a look when I get back to the office. I did run verifier on all the
> > drivers a week or so back (while running vbd plug/unplug tests) but
> > there have been a couple of changes since then.
> >
> > Paul
> >
> No problem. I attached some more logs. The last one was during system
> shutdown, after that the OS failed to boot (probably corrupted
> filesystem since the BSOD itself seemed to indicate that). I think every
> time there is a BLKIF_RSP_ERROR somewhere but I'm not yet familiar with
> Xen PV device interfaces so not sure what that means.
> 

Any error on the backend is pretty suspicious. Are you still seeing them? The 
other thing to check for is that (because I messed with all this code recently) 
you are not ending up with a PV disk and an emulated disk at the same time. If 
you do then Windows will mount both instances and they will corrupt each other 
(since they are backed by the same image).

  Paul

> In the meantime I've run more tests on my modified xeniface driver to
> make sure it's not contributing to these issues but everything seemed to
> be fine there.
> 
> --
> RafaÅ WojdyÅa
> Qubes Tools for Windows developer
> https://www.qubes-os.org/
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