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Re: [PATCH v3 01/41] x86/tsc: Add a standalone helpers for getting TSC info from CPUID.0x15
- To: Sean Christopherson <seanjc@xxxxxxxxxx>, Kiryl Shutsemau <kas@xxxxxxxxxx>, Paolo Bonzini <pbonzini@xxxxxxxxxx>, "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>, Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>, Wei Liu <wei.liu@xxxxxxxxxx>, Dexuan Cui <decui@xxxxxxxxxxxxx>, Long Li <longli@xxxxxxxxxxxxx>, Ajay Kaher <ajay.kaher@xxxxxxxxxxxx>, Alexey Makhalov <alexey.makhalov@xxxxxxxxxxxx>, Jan Kiszka <jan.kiszka@xxxxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxx>, John Stultz <jstultz@xxxxxxxxxx>
- From: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
- Date: Wed, 20 May 2026 19:59:10 +0100
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- Cc: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>, Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>, Broadcom internal kernel review list <bcm-kernel-feedback-list@xxxxxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Stephen Boyd <sboyd@xxxxxxxxxx>, x86@xxxxxxxxxx, linux-coco@xxxxxxxxxxxxxxx, kvm@xxxxxxxxxxxxxxx, linux-hyperv@xxxxxxxxxxxxxxx, virtualization@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, Michael Kelley <mhklinux@xxxxxxxxxxx>, Tom Lendacky <thomas.lendacky@xxxxxxx>, Nikunj A Dadhania <nikunj@xxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>
- Delivery-date: Wed, 20 May 2026 18:59:27 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Fri, 2026-05-15 at 12:19 -0700, Sean Christopherson wrote:
> Extract retrieval of TSC frequency information from CPUID into standalone
> helpers so that TDX guest support can reuse the logic. Provide a version
> that includes the multiplier math as TDX 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.
>
> Opportunsitically drop native_calibrate_tsc()'s "== 0" and "!= 0" checks
> in favor of the kernel's preferred style.
"Opportunistically" ? Now that looks wrong too...
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Reviewed-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
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