From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
"K. Y. Srinivasan" <kys@microsoft.com>, X86 ML <x86@kernel.org>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Dexuan Cui <decui@microsoft.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
devel@linuxdriverproject.org,
Linux Virtualization <virtualization@lists.linux-foundation.org>
Subject: Re: [PATCH v2 0/3] x86/vdso: Add Hyper-V TSC page clocksource support
Date: Fri, 17 Feb 2017 18:55:02 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.20.1702171853480.3536@nanos> (raw)
In-Reply-To: <CALCETrXB8CufQujLAg6bbq=DGAMUE293CF7L4Kp+mCSoNWyuBg@mail.gmail.com>
On Fri, 17 Feb 2017, Andy Lutomirski wrote:
> On Fri, Feb 17, 2017 at 2:14 AM, Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
> > Not only. As far as I understand (and I *think* K. Y. pointed this out)
> > when VM is migrating to another host TSC page clocksource is disabled for
> > extended period of time so we're better off reading from MSR than
> > looping here. With regards to VDSO this means reverting to doing normal
> > syscall.
>
> That's a crappy design. The guest really ought to be able to
> distinguish "busy, try again" from "bail and use MSR".
>
> Thomas, I can see valid reasons why the hypervisor might want to
> temporarily disable shared page-based timing, but I think it's silly
> that it's conflated with indicating "retry".
It's beyond silly if that's the case.
> But if this is indeed the ABI, we're stuck with it.
No argument.
prev parent reply other threads:[~2017-02-17 17:55 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-14 12:44 Vitaly Kuznetsov
2017-02-14 12:44 ` [PATCH v2 1/3] x86/hyperv: implement hv_get_tsc_page() Vitaly Kuznetsov
2017-02-14 12:44 ` [PATCH v2 2/3] x86/hyperv: move TSC reading method to asm/mshyperv.h Vitaly Kuznetsov
2017-02-14 12:44 ` [PATCH v2 3/3] x86/vdso: Add VCLOCK_HVCLOCK vDSO clock read method Vitaly Kuznetsov
2017-02-14 14:46 ` [PATCH v2 0/3] x86/vdso: Add Hyper-V TSC page clocksource support KY Srinivasan
2017-02-14 14:56 ` Thomas Gleixner
2017-02-14 15:50 ` Vitaly Kuznetsov
2017-02-14 17:34 ` Andy Lutomirski
2017-02-15 14:01 ` Vitaly Kuznetsov
2017-02-16 17:50 ` Thomas Gleixner
2017-02-17 10:14 ` Vitaly Kuznetsov
2017-02-17 10:35 ` Thomas Gleixner
2017-02-17 17:02 ` Andy Lutomirski
2017-02-17 17:55 ` Thomas Gleixner [this message]
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