From: Sean Christopherson <seanjc@google.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Paul Durrant <paul@xen.org>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Valentin Schneider <vschneid@redhat.com>,
Shuah Khan <shuah@kernel.org>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
jalliste@amazon.co.uk, sveith@amazon.de, zide.chen@intel.com,
Dongli Zhang <dongli.zhang@oracle.com>,
Chenyi Qiang <chenyi.qiang@intel.com>
Subject: Re: [RFC PATCH v3 19/21] KVM: x86: Avoid periodic KVM clock updates in master clock mode
Date: Thu, 15 Aug 2024 21:33:01 -0700 [thread overview]
Message-ID: <Zr7WfbCBPhoNMukJ@google.com> (raw)
In-Reply-To: <20240522001817.619072-20-dwmw2@infradead.org>
On Wed, May 22, 2024, David Woodhouse wrote:
> From: David Woodhouse <dwmw@amazon.co.uk>
>
> When the KVM clock is in master clock mode, updating the KVM clock is
> pointless.
Please explain why it's pointless. I almost feel bad asking you to elaborate
since you've written wonderful changelogs for so many other patches, but far too
many of the (historical) kvmclock commits assume the reader is some omniscient
being, and it's definitely contributed to things getting into such a mess state.
> Let the periodic work 'expire', and start it running again
> from kvm_end_pvclock_update() if the master clock mode is ever turned
> off again.
next prev parent reply other threads:[~2024-08-16 4:33 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-22 0:16 [RFC PATCH v3 00/21] Cleaning up the KVM clock mess David Woodhouse
2024-05-22 0:16 ` [RFC PATCH v3 01/21] KVM: x86/xen: Do not corrupt KVM clock in kvm_xen_shared_info_init() David Woodhouse
2024-05-22 0:16 ` [RFC PATCH v3 02/21] KVM: x86: Improve accuracy of KVM clock when TSC scaling is in force David Woodhouse
2024-08-13 17:50 ` Sean Christopherson
2024-05-22 0:16 ` [RFC PATCH v3 03/21] KVM: x86: Add KVM_[GS]ET_CLOCK_GUEST for accurate KVM clock migration David Woodhouse
2024-05-22 0:16 ` [RFC PATCH v3 04/21] UAPI: x86: Move pvclock-abi to UAPI for x86 platforms David Woodhouse
2024-05-24 13:14 ` Paul Durrant
2024-08-13 18:07 ` Sean Christopherson
2024-05-22 0:17 ` [RFC PATCH v3 05/21] KVM: selftests: Add KVM/PV clock selftest to prove timer correction David Woodhouse
2024-08-13 18:55 ` Sean Christopherson
2024-05-22 0:17 ` [RFC PATCH v3 06/21] KVM: x86: Explicitly disable TSC scaling without CONSTANT_TSC David Woodhouse
2024-05-22 0:17 ` [RFC PATCH v3 07/21] KVM: x86: Add KVM_VCPU_TSC_SCALE and fix the documentation on TSC migration David Woodhouse
2024-08-14 1:52 ` Sean Christopherson
2024-05-22 0:17 ` [RFC PATCH v3 08/21] KVM: x86: Avoid NTP frequency skew for KVM clock on 32-bit host David Woodhouse
2024-08-14 1:57 ` Sean Christopherson
2024-05-22 0:17 ` [RFC PATCH v3 09/21] KVM: x86: Fix KVM clock precision in __get_kvmclock() David Woodhouse
2024-05-24 13:20 ` Paul Durrant
2024-08-14 2:58 ` Sean Christopherson
2024-05-22 0:17 ` [RFC PATCH v3 10/21] KVM: x86: Fix software TSC upscaling in kvm_update_guest_time() David Woodhouse
2024-05-24 13:26 ` Paul Durrant
2024-08-14 4:57 ` Sean Christopherson
2024-05-22 0:17 ` [RFC PATCH v3 11/21] KVM: x86: Simplify and comment kvm_get_time_scale() David Woodhouse
2024-05-24 13:53 ` Paul Durrant
2024-08-15 15:46 ` Sean Christopherson
2024-05-22 0:17 ` [RFC PATCH v3 12/21] KVM: x86: Remove implicit rdtsc() from kvm_compute_l1_tsc_offset() David Woodhouse
2024-05-24 13:56 ` Paul Durrant
2024-08-15 15:52 ` Sean Christopherson
2024-05-22 0:17 ` [RFC PATCH v3 13/21] KVM: x86: Improve synchronization in kvm_synchronize_tsc() David Woodhouse
2024-05-24 14:03 ` Paul Durrant
2024-08-15 16:00 ` Sean Christopherson
2024-05-22 0:17 ` [RFC PATCH v3 14/21] KVM: x86: Kill cur_tsc_{nsec,offset,write} fields David Woodhouse
2024-05-24 14:05 ` Paul Durrant
2024-08-15 16:30 ` Sean Christopherson
2024-05-22 0:17 ` [RFC PATCH v3 15/21] KVM: x86: Allow KVM master clock mode when TSCs are offset from each other David Woodhouse
2024-05-24 14:10 ` Paul Durrant
2024-08-16 2:38 ` Sean Christopherson
2024-05-22 0:17 ` [RFC PATCH v3 16/21] KVM: x86: Factor out kvm_use_master_clock() David Woodhouse
2024-05-24 14:13 ` Paul Durrant
2024-08-15 17:12 ` Sean Christopherson
2024-05-22 0:17 ` [RFC PATCH v3 17/21] KVM: x86: Avoid global clock update on setting KVM clock MSR David Woodhouse
2024-05-24 14:14 ` Paul Durrant
2024-08-16 4:28 ` Sean Christopherson
2024-05-22 0:17 ` [RFC PATCH v3 18/21] KVM: x86: Avoid gratuitous global clock reload in kvm_arch_vcpu_load() David Woodhouse
2024-05-24 14:16 ` Paul Durrant
2024-08-15 17:31 ` Sean Christopherson
2024-05-22 0:17 ` [RFC PATCH v3 19/21] KVM: x86: Avoid periodic KVM clock updates in master clock mode David Woodhouse
2024-05-24 14:18 ` Paul Durrant
2024-08-16 4:33 ` Sean Christopherson [this message]
2024-05-22 0:17 ` [RFC PATCH v3 20/21] KVM: x86/xen: Prevent runstate times from becoming negative David Woodhouse
2024-05-24 14:21 ` Paul Durrant
2024-08-16 4:39 ` Sean Christopherson
2024-08-20 10:22 ` David Woodhouse
2024-08-20 15:08 ` Steven Rostedt
2024-08-20 15:42 ` David Woodhouse
2024-05-22 0:17 ` [RFC PATCH v3 21/21] sched/cputime: Cope with steal time going backwards or negative David Woodhouse
2024-05-24 14:25 ` Paul Durrant
2024-07-02 14:09 ` Shrikanth Hegde
2024-08-16 4:35 ` Sean Christopherson
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