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From: Paul Durrant <xadimgnik@gmail.com>
Message-ID: <a7f58b0d-6145-4f56-8d53-8a90bee84fe9@xen.org>
Date: Fri, 24 May 2024 14:53:05 +0100
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Subject: Re: [RFC PATCH v3 11/21] KVM: x86: Simplify and comment
 kvm_get_time_scale()
To: David Woodhouse <dwmw2@infradead.org>, kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>, Jonathan Corbet <corbet@lwn.net>,
 Sean Christopherson <seanjc@google.com>, 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>,
 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>
References: <20240522001817.619072-1-dwmw2@infradead.org>
 <20240522001817.619072-12-dwmw2@infradead.org>
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On 22/05/2024 01:17, David Woodhouse wrote:
> From: David Woodhouse <dwmw@amazon.co.uk>
> 
> Commit 3ae13faac400 ("KVM: x86: pass kvm_get_time_scale arguments in hertz")
> made this function take 64-bit values in Hz rather than 32-bit kHz. Thus
> making it entrely pointless to shadow its arguments into local 64-bit
> variables. Just use scaled_hz and base_hz directly.
> 
> Also rename the 'tps32' variable to 'base32', having utterly failed to
> think of any reason why it might have been called that in the first place.
> This could probably have been eliminated too, but it helps to make the
> code clearer and *might* just help a naïve 32-bit compiler realise that it
> doesn't need to do full 64-bit shifts.
> 
> Having taken the time to reverse-engineer the function, add some comments
> explaining it.
> 
> No functional change intended.
> 
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> ---
>   arch/x86/kvm/x86.c | 60 ++++++++++++++++++++++++++++++++++++----------
>   1 file changed, 47 insertions(+), 13 deletions(-)
> 

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