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From: Sean Christopherson <seanjc@google.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Dongli Zhang <dongli.zhang@oracle.com>,
	Joe Jin <joe.jin@oracle.com>,
	x86@kernel.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org, pbonzini@redhat.com,
	tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
	dave.hansen@linux.intel.com
Subject: Re: [PATCH RFC 1/1] KVM: x86: add param to update master clock periodically
Date: Tue, 3 Oct 2023 17:10:22 -0700	[thread overview]
Message-ID: <ZRytbih4TUVkEhLC@google.com> (raw)
In-Reply-To: <96ceb6a6e9c380d329e8cd556ad13a2fcd554882.camel@infradead.org>

On Tue, Oct 03, 2023, David Woodhouse wrote:
> On Mon, 2023-10-02 at 17:53 -0700, Sean Christopherson wrote:
> > 
> > This is *very* lightly tested, as in it compiles and doesn't explode, but that's
> > about all I've tested.
> 
> I don't think it's working, if I understand what it's supposed to be
> doing.

...

> When I run xen_shinfo_test, the kvmclock still drifts from the
> "monotonic_raw" I get from kvm_get_time_and_clockread(), even with your
> patch.

It "works", in that it does what I intended it to do.  What I missed, and what's
obvious in hindsight, is that the timekeeping code doesn't *just* update what KVM
uses as the "base" when there "big events" like suspend/resume, the timekeeping
code updates the base clock on every tick.

My hack only smoothed away the delta, it didn't address the time that had gotten
moved into the base.  I though the base would be stable if the host was in a
steady state, but see above...

      reply	other threads:[~2023-10-04  0:10 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-26 23:06 [PATCH RFC 1/1] KVM: x86: add param to update master clock periodically Dongli Zhang
2023-09-27  0:29 ` Joe Jin
2023-09-27  0:36   ` Dongli Zhang
2023-09-28 16:18     ` Sean Christopherson
2023-09-29 20:15       ` Dongli Zhang
2023-10-02  8:33         ` David Woodhouse
2023-10-02 16:37           ` Sean Christopherson
2023-10-02 17:17             ` Dongli Zhang
2023-10-02 18:18               ` Sean Christopherson
2023-10-02 21:06                 ` Peter Zijlstra
2023-10-02 21:16                   ` Peter Zijlstra
2023-10-02 18:16             ` David Woodhouse
2023-10-03  0:53               ` Sean Christopherson
2023-10-03  1:32                 ` Dongli Zhang
2023-10-03  1:49                   ` Sean Christopherson
2023-10-03  2:07                     ` Dongli Zhang
2023-10-03 21:00                       ` Sean Christopherson
2023-10-03  5:54                 ` David Woodhouse
2023-10-04  0:04                   ` Sean Christopherson
2023-10-04 10:01                     ` David Woodhouse
2023-10-04 18:06                       ` Sean Christopherson
2023-10-04 19:13                         ` Dongli Zhang
2023-10-11  0:20                           ` Sean Christopherson
2023-10-11  7:18                             ` David Woodhouse
2023-10-13 18:07                               ` Sean Christopherson
2023-10-13 18:21                                 ` David Woodhouse
2023-10-13 19:02                                   ` Sean Christopherson
2023-10-13 19:12                                     ` David Woodhouse
2023-10-13 20:03                                       ` Sean Christopherson
2023-10-13 20:12                                 ` Dongli Zhang
2023-10-13 23:26                                   ` Sean Christopherson
2023-10-14  9:49                                     ` David Woodhouse
2023-10-16 15:47                                       ` Dongli Zhang
2023-10-16 16:25                                         ` David Woodhouse
2023-10-16 17:04                                           ` Dongli Zhang
2023-10-16 18:49                                           ` Sean Christopherson
2023-10-16 22:04                                             ` Dongli Zhang
2023-10-16 22:48                                               ` Sean Christopherson
2023-10-17 16:18                                                 ` Dongli Zhang
2023-10-03  9:12                 ` David Woodhouse
2023-10-04  0:07                   ` Sean Christopherson
2023-10-04  8:06                     ` David Woodhouse
2023-10-03 14:29                 ` David Woodhouse
2023-10-04  0:10                   ` Sean Christopherson [this message]

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