From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Dexuan Cui <decui@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
"x86@kernel.org" <x86@kernel.org>, Ingo Molnar <mingo@redhat.com>,
"H. Peter Anvin" <hpa@zytor.com>,
KY Srinivasan <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"devel@linuxdriverproject.org" <devel@linuxdriverproject.org>,
"virtualization@lists.linux-foundation.org"
<virtualization@lists.linux-foundation.org>
Subject: Re: [PATCH 2/2] x86/vdso: Add VCLOCK_HVCLOCK vDSO clock read method
Date: Mon, 13 Feb 2017 20:28:21 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.20.1702132027300.3790@nanos> (raw)
In-Reply-To: <CALCETrX3UkxNkAtyL+fk=HEtBRmd3GCkw+qLur4aVgp7rn4WCA@mail.gmail.com>
On Mon, 13 Feb 2017, Andy Lutomirski wrote:
> On Sun, Feb 12, 2017 at 11:49 PM, Dexuan Cui <decui@microsoft.com> wrote:
> >> 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.
>
> 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
next prev parent reply other threads:[~2017-02-13 19:28 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-09 14:10 [PATCH 0/2] x86/vdso: Add Hyper-V TSC page clocksource support Vitaly Kuznetsov
2017-02-09 14:10 ` [PATCH 1/2] hyperv: implement hv_get_tsc_page() Vitaly Kuznetsov
2017-02-09 18:24 ` Stephen Hemminger
2017-02-09 20:14 ` Thomas Gleixner
2017-02-09 23:17 ` Stephen Hemminger
2017-02-09 14:10 ` [PATCH 2/2] x86/vdso: Add VCLOCK_HVCLOCK vDSO clock read method Vitaly Kuznetsov
2017-02-09 17:08 ` Thomas Gleixner
2017-02-09 18:27 ` Stephen Hemminger
2017-02-10 12:25 ` Vitaly Kuznetsov
2017-02-10 12:28 ` Thomas Gleixner
2017-02-10 16:31 ` Stephen Hemminger
2017-02-10 18:01 ` Thomas Gleixner
2017-02-13 7:49 ` Dexuan Cui
2017-02-13 9:27 ` Thomas Gleixner
2017-02-13 19:06 ` Andy Lutomirski
2017-02-13 19:28 ` Thomas Gleixner [this message]
2017-02-09 20:45 ` KY Srinivasan
2017-02-09 22:55 ` Andy Lutomirski
2017-02-09 23:15 ` Stephen Hemminger
2017-02-10 12:15 ` Vitaly Kuznetsov
2017-02-10 11:06 ` Vitaly Kuznetsov
2017-02-10 11:15 ` Thomas Gleixner
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