RE: [PATCH 2/2] x86/vdso: Add VCLOCK_HVCLOCK vDSO clock read method

Dexuan Cui via Virtualization
2017-02-13T07:49:26Z

> From: Thomas Gleixner [mailto:tglx@linutronix.de]
> Sent: Saturday, February 11, 2017 02:02
> ...
> That's important if the stuff happens cross CPU. If the update happens on
> the same CPU then this is a different story and as there are VMexits
> involved they might provide the required ordering already. But I can't tell
> as I have no idea how that host side thing is done.
>
> tglx

IMO Hyper-V TSC page clocksource here seems pretty similar to KVM's pvclock,
So I would guess "the structure is only updated just before reentering the guest
after some VM event" (https://rwmj.wordpress.com/2010/10/15/kvm-pvclock/),
that is, the update should happen on the same CPU, I guess.

Thanks,
-- Dexuan