On Mon, 13 Feb 2017, Andy Lutomirski wrote: > On Sun, Feb 12, 2017 at 11:49 PM, Dexuan Cui <decui@xxxxxxxxxxxxx> wrote: > >> From: Thomas Gleixner [mailto:tglx@xxxxxxxxxxxxx] > >> 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. > > If the patch is correct, there is one of these shared by all vCPUs, so > this is not a sufficient explanation. Right, because that's ony ONE TSC page for the whole guest and then the seq stuff really lacks barriers. Thanks, tglx _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
