linux-kernel - Re: [PATCH 08/10] KVM: x86: Remove periodic global clock updates

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Message-ID: <15a9176e-9221-44b9-b8df-910c0c16ddc2@xen.org>
Date: Fri, 19 Apr 2024 16:55:47 +0100
From: Paul Durrant <xadimgnik@...il.com>
To: David Woodhouse <dwmw2@...radead.org>, kvm@...r.kernel.org
Cc: Paolo Bonzini <pbonzini@...hat.com>, Jonathan Corbet <corbet@....net>,
 Sean Christopherson <seanjc@...gle.com>, Thomas Gleixner
 <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
 Shuah Khan <shuah@...nel.org>, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
 Oliver Upton <oliver.upton@...ux.dev>, Marcelo Tosatti
 <mtosatti@...hat.com>, jalliste@...zon.co.uk, sveith@...zon.de
Subject: Re: [PATCH 08/10] KVM: x86: Remove periodic global clock updates

On 18/04/2024 20:34, David Woodhouse wrote:
> From: David Woodhouse <dwmw@...zon.co.uk>
> 
> This effectively reverts commit 332967a3eac0 ("x86: kvm: introduce
> periodic global clock updates"). The periodic update was introduced to
> propagate NTP corrections to the guest KVM clock, when the KVM clock was
> based on CLOCK_MONOTONIC.
> 
> However, commit 53fafdbb8b21 ("KVM: x86: switch KVMCLOCK base to
> monotonic raw clock") switched to using CLOCK_MONOTONIC_RAW as the basis
> for the KVM clock, avoiding the NTP frequency skew altogether.
> 
> So the periodic update serves no purpose. Remove it.
> 
> Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
> ---
>   arch/x86/kvm/x86.c | 25 -------------------------
>   1 file changed, 25 deletions(-)
> 

Reviewed-by: Paul Durrant <paul@....org>