From: Thomas Gleixner <tglx@linutronix.de>
To: Dexuan Cui <decui@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
"x86@kernel.org" <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Andy Lutomirski <luto@amacapital.net>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
"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 10:27:18 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.20.1702131023190.3619@nanos> (raw)
In-Reply-To: <MWHPR03MB266952220A7E1FA0F2D38453BF590@MWHPR03MB2669.namprd03.prod.outlook.com>
On Mon, 13 Feb 2017, Dexuan Cui 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.
> >
>
> 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.
Guessing does not help much. There are a gazillion ways to implement such a
thing. I'm sure that there exists proper documentation of the mechanism
inside your company.
Thanks,
tglx
next prev parent reply other threads:[~2017-02-13 9:27 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20170209141052.18694-1-vkuznets@redhat.com>
2017-02-09 14:10 ` [PATCH 1/2] hyperv: implement hv_get_tsc_page() Vitaly Kuznetsov
2017-02-09 14:10 ` [PATCH 2/2] x86/vdso: Add VCLOCK_HVCLOCK vDSO clock read method Vitaly Kuznetsov
[not found] ` <20170209141052.18694-3-vkuznets@redhat.com>
2017-02-09 17:08 ` Thomas Gleixner
[not found] ` <alpine.DEB.2.20.1702091806400.3604@nanos>
2017-02-09 18:27 ` Stephen Hemminger via Virtualization
2017-02-10 12:25 ` Vitaly Kuznetsov
2017-02-10 12:28 ` Thomas Gleixner
2017-02-10 16:31 ` Stephen Hemminger via Virtualization
[not found] ` <BLUPR0301MB2098E1283D42BD2C3772D839CC440@BLUPR0301MB2098.namprd03.prod.outlook.com>
2017-02-10 18:01 ` Thomas Gleixner
2017-02-13 7:49 ` Dexuan Cui via Virtualization
2017-02-13 9:27 ` Thomas Gleixner [this message]
2017-02-13 19:06 ` Andy Lutomirski
2017-02-13 19:28 ` Thomas Gleixner
2017-02-09 20:45 ` KY Srinivasan via Virtualization
[not found] ` <DM5PR03MB24903D71121176FFAED30E33A0450@DM5PR03MB2490.namprd03.prod.outlook.com>
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
[not found] ` <20170209141052.18694-2-vkuznets@redhat.com>
2017-02-09 18:24 ` [PATCH 1/2] hyperv: implement hv_get_tsc_page() Stephen Hemminger via Virtualization
2017-02-09 20:14 ` Thomas Gleixner
2017-02-09 23:17 ` Stephen Hemminger
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