linux-kernel - Re: [PATCH 01/16] x86/tsc: Add a standalone helpers for getting TSC info from CPUID.0x15

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Message-ID: <855xlra7yh.fsf@amd.com>
Date: Mon, 3 Feb 2025 05:55:02 +0000
From: Nikunj A Dadhania <nikunj@....com>
To: 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>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Juergen Gross
	<jgross@...e.com>, "K. Y. Srinivasan" <kys@...rosoft.com>, Haiyang Zhang
	<haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, Dexuan Cui
	<decui@...rosoft.com>, Ajay Kaher <ajay.kaher@...adcom.com>, "Alexey
 Makhalov" <alexey.amakhalov@...adcom.com>, Jan Kiszka
	<jan.kiszka@...mens.com>, Paolo Bonzini <pbonzini@...hat.com>, "Andy
 Lutomirski" <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>
CC: <linux-kernel@...r.kernel.org>, <linux-coco@...ts.linux.dev>,
	<virtualization@...ts.linux.dev>, <linux-hyperv@...r.kernel.org>,
	<jailhouse-dev@...glegroups.com>, <kvm@...r.kernel.org>,
	<xen-devel@...ts.xenproject.org>, Sean Christopherson <seanjc@...gle.com>,
	Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [PATCH 01/16] x86/tsc: Add a standalone helpers for getting TSC
 info from CPUID.0x15

Sean Christopherson <seanjc@...gle.com> writes:
> Extract retrieval of TSC frequency information from CPUID into standalone
> helpers so that TDX guest support and kvmlock can reuse the logic.  Provide

s/kvmlock/kvmclock

> a version that includes the multiplier math as TDX in particular does NOT
> want to use native_calibrate_tsc()'s fallback logic that derives the TSC
> frequency based on CPUID.0x16 when the core crystal frequency isn't known.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---

...

> +
> +static inline int cpuid_get_tsc_freq(unsigned int *tsc_khz,
> +				     unsigned int *crystal_khz)

Should we add this in patch 6/16 where it is being used for the first time ?

Regards
Nikunj