From: Thomas Gleixner <tglx@linutronix.de>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: kvm@vger.kernel.org, x86@kernel.org,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Ingo Molnar" <mingo@redhat.com>,
"H. Peter Anvin" <hpa@zytor.com>,
"K. Y. Srinivasan" <kys@microsoft.com>,
"Haiyang Zhang" <haiyangz@microsoft.com>,
"Stephen Hemminger" <sthemmin@microsoft.com>,
"Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>,
"Andy Lutomirski" <luto@kernel.org>,
"Mohammed Gamal" <mmorsy@redhat.com>,
"Cathy Avery" <cavery@redhat.com>,
"Roman Kagan" <rkagan@virtuozzo.com>,
linux-kernel@vger.kernel.org, devel@linuxdriverproject.org
Subject: Re: [PATCH v3 3/7] x86/hyper-v: reenlightenment notifications support
Date: Tue, 16 Jan 2018 19:33:18 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.20.1801161932590.2366@nanos> (raw)
In-Reply-To: <20180116182700.1042-4-vkuznets@redhat.com>
On Tue, 16 Jan 2018, Vitaly Kuznetsov wrote:
> Hyper-V supports Live Migration notification. This is supposed to be used
> in conjunction with TSC emulation: when we are migrated to a host with
> different TSC frequency for some short period host emulates our accesses
> to TSC and sends us an interrupt to notify about the event. When we're
> done updating everything we can disable TSC emulation and everything will
> start working fast again.
>
> We didn't need these notifications before as Hyper-V guests are not
> supposed to use TSC as a clocksource: in Linux we even mark it as unstable
> on boot. Guests normally use 'tsc page' clocksouce and host updates its
> values on migrations automatically.
>
> Things change when we want to run nested virtualization: even when we pass
> through PV clocksources (kvm-clock or tsc page) to our guests we need to
> know TSC frequency and when it changes.
>
> Hyper-V Top Level Functional Specification (as of v5.0b) wrongly specifies
> EAX:BIT(12) of CPUID:0x40000009 as the feature identification bit. The
> right one to check is EAX:BIT(13) of CPUID:0x40000003. I was assured that
> the fix in on the way.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
next prev parent reply other threads:[~2018-01-16 18:33 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-16 18:26 [PATCH v3 0/7] x86/kvm/hyperv: stable clocksorce for L2 guests when running nested KVM on Hyper-V Vitaly Kuznetsov
2018-01-16 18:26 ` [PATCH v3 1/7] x86/hyper-v: check for required priviliges in hyperv_init() Vitaly Kuznetsov
2018-01-16 18:26 ` [PATCH v3 2/7] x86/hyper-v: add a function to read both TSC and TSC page value simulateneously Vitaly Kuznetsov
2018-01-16 18:26 ` [PATCH v3 3/7] x86/hyper-v: reenlightenment notifications support Vitaly Kuznetsov
2018-01-16 18:33 ` Thomas Gleixner [this message]
2018-01-19 10:21 ` kbuild test robot
2018-01-19 10:47 ` Vitaly Kuznetsov
2018-01-20 7:48 ` Thomas Gleixner
2018-01-22 1:22 ` Michael Kelley (EOSG)
2018-01-22 12:06 ` Vitaly Kuznetsov
2018-01-23 13:41 ` Vitaly Kuznetsov
2018-01-23 14:02 ` Michael Kelley (EOSG)
2018-01-23 14:07 ` Vitaly Kuznetsov
2018-01-22 10:41 ` Vitaly Kuznetsov
2018-01-19 11:11 ` kbuild test robot
2018-01-16 18:26 ` [PATCH v3 4/7] x86/hyper-v: redirect reenlightment notifications on CPU offlining Vitaly Kuznetsov
2018-01-16 18:31 ` Thomas Gleixner
2018-01-16 18:26 ` [PATCH v3 5/7] x86/irq: Count Hyper-V reenlightenment interrupts Vitaly Kuznetsov
2018-01-16 18:32 ` Thomas Gleixner
2018-01-16 18:26 ` [PATCH v3 6/7] x86/kvm: pass stable clocksource to guests when running nested on Hyper-V Vitaly Kuznetsov
2018-01-16 18:27 ` [PATCH v3 7/7] x86/kvm: support Hyper-V reenlightenment Vitaly Kuznetsov
2018-01-19 11:15 ` kbuild test robot
2018-01-19 11:15 ` [RFC PATCH] x86/kvm: kvm_hyperv_tsc_notifier() can be static kbuild test robot
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