linux-kernel - Re: system time goes weird in kvm guest after host suspend/resume

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Message-ID: <CAJfpegsjd+FJ0ZNHJ_qzJo0Dx22ZaWh-WZ48f94Z3AUXbJfYYQ@mail.gmail.com>
Date:   Fri, 29 May 2020 11:51:30 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org
Subject: Re: system time goes weird in kvm guest after host suspend/resume

On Thu, May 28, 2020 at 10:43 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> Miklos Szeredi <miklos@...redi.hu> writes:
> > Bisected it to:
> >
> > b95a8a27c300 ("x86/vdso: Use generic VDSO clock mode storage")
> >
> > The effect observed is that after the host is resumed, the clock in
> > the guest is somewhat in the future and is stopped.  I.e. repeated
> > date(1) invocations show the same time.
>
> TBH, the bisect does not make any sense at all. It's renaming the
> constants and moving the storage space and I just read it line for line
> again that the result is equivalent. I'll have a look once the merge
> window dust settles a bit.

Yet, reverting just that single commit against latest linus tree fixes
the issue.  Which I think is a pretty good indication that that commit
*is* doing something.

The jump forward is around 35 minutes; that seems to be consistent as well.

Thanks,
Miklos