Re: Fwd: [BUG] Windows is frozen after restore from snapshot

[Tamas K Lengyel <tamas.k.lengyel@xxxxxxxxx>]

On Fri, Apr 23, 2021 at 12:19 PM Sergey Kovalev <valor@xxxxxxx> wrote:
>
>
> 23.04.2021 18:08, Roger Pau Monné пишет:
> > On Fri, Apr 23, 2021 at 01:22:34PM +0300, Sergey Kovalev wrote:
> >> # Abstract
> >>
> >> After `xl save win win.mem` and then `xl restore win.hvm win.mem`
> >> the Windows 10 VM remain frozen for about a minute. After the
> >> minute it becomes responsive.
> >>
> >> During the freeze the OS remains semi-responsive: on `Ctrl+Shift+Esc`
> >> press the wait cursor appears (blue circle indicator).
> >>
> >> This is an intermittent fault been reproduced only twice.
> >>
> >> # Technical notes
> >>
> >> It have been noticed that there were no timer interrupts during
> >> the freeze.
> >>
> >> zaytsevgu@xxxxxxxxx has debugged the received Xen state file and
> >> noticed that the flag HPET_TN_PERIODIC been set after unfreeze.
> >>
> >> Based on that he provided two Python scripts: one to check the
> >> value and one to patch it.
> >>
> >> Both "broken" state files we have been detected and patched
> >> successfully.
> >>
> >> # Other information
> >>
> >> ## Target machine
> >>
> >> ```bash
> >> $ uname -a
> >> Linux localhost 5.4.0-66-generic #74~18.04.2-Ubuntu SMP
> >> Fri Feb 5 11:17:31 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
> >> ```
> >>
> >> ## Xen version
> >>
> >> Build from source on tag RELEASE-4.12.4
> >>
> >> ## OS version
> >>
> >> * Windows 10 build 1803 x64
> >
> > Do you also run other versions of Windows, and in which case I assume
> > you have never seen the issue on those, or it's this specific version
> > the only that you use?
> >
> > Thanks, Roger.
> >
>
> We use Windows 7 SP1 x86/x64, Windows 8.1 update1 and
> Windows 10 1803 x64.
>
> The Windows 10 is the only one affected by the bug at
> the time.

I can confirm that I have ran into this issue as well in the past, but
never had time to dig deeper into the root cause. I may add that with
snapshots taken of Windows 10 on Xen 4.14 or 4.15 and using those for
restoring I haven't seen it happen yet. The Win10 version didn't
change on my end, only the hypervisor got upgraded. So this may be a
bug that got fixed in newer Xen versions.

Tamas