Re: [patch 0/3] vdso: Unbreak VDSO with PV and HyperV clocksources

[Miklos Szeredi]

On Sun, Jun 7, 2020 at 11:36 AM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>
> Miklos reported [1] that the recent VDSO changes broke paravirt clocksource
> based VDSO in the case that the clocksource is invalidated by the
> hypervisor which happens after a suspend/resume cycle of the host.
>
> The result is a stale clocksource which is about 2200 seconds ahead of the
> actual time and jumps forward by 2200 seconds once 2200 seconds have
> elapsed.
>
> The reason for this is the core code change which optimized the VDSO
> clocksource validation by checking for the clocksource mode instead of
> using the rather subtle check for the clocksource read return value whether
> it has bit 63 set.
>
> For some reason my brain blanked when doing that change, even if I should
> have known better.
>
> The following series restores the previous behaviour but preserves the
> initially intended optimization for architectures which don't need that PV
> handling.

Thanks for fixing.

Tested-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>

Miklos