From: David Woodhouse <dwmw2@infradead.org>
To: Sean Christopherson <seanjc@google.com>
Cc: Paul Durrant <pdurrant@amazon.co.uk>,
Fred Griffoul <fgriffo@amazon.co.uk>,
Colin Percival <cperciva@tarsnap.com>,
Paolo Bonzini <pbonzini@redhat.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" <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Graf (AWS), Alexander" <graf@amazon.de>,
Ajay Kaher <ajay.kaher@broadcom.com>,
Alexey Makhalov <alexey.makhalov@broadcom.com>
Subject: Re: [PATCH v2 0/3] Support "generic" CPUID timing leaf as KVM guest and host
Date: Thu, 04 Sep 2025 14:14:57 +0200 [thread overview]
Message-ID: <4a3be390fe559de0bd5c61d24853d88f96a6ab6a.camel@infradead.org> (raw)
In-Reply-To: <aLl_MAk9AT5hRuoS@google.com>
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On Thu, 2025-09-04 at 04:59 -0700, Sean Christopherson wrote:
>
> I thought the original problem being solved was that the _guest_ doesn't know the
> effective TSC frequency? Userspace can already get the effectively TSC frequency
> via KVM_GET_TSC_KHZ, why do we need another uAPI to provide that? (Honest question,
> I feel like I'm missing something)
I believe that KVM_GET_TSC_KHZ returns what userspace *asked* for the
TSC frequency to be (vcpu->arch.virtual_tsc_khz), not what it actually
ended up being based on the measured host frequency and the available
scaling granularity (vcpu->hw_tsc_khz).
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next prev parent reply other threads:[~2025-09-04 12:15 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-16 10:09 [PATCH v2 0/3] Support "generic" CPUID timing leaf as KVM guest and host David Woodhouse
2025-08-16 10:10 ` [PATCH v2 1/3] KVM: x86: Restore caching of KVM CPUID base David Woodhouse
2025-08-16 10:10 ` [PATCH v2 2/3] KVM: x86: Provide TSC frequency in "generic" timing infomation CPUID leaf David Woodhouse
2025-08-16 10:10 ` [PATCH v2 3/3] x86/kvm: Obtain TSC frequency from CPUID if present David Woodhouse
2025-08-21 16:26 ` [PATCH v2 0/3] Support "generic" CPUID timing leaf as KVM guest and host Sean Christopherson
2025-08-21 17:37 ` David Woodhouse
2025-08-21 19:27 ` Sean Christopherson
2025-08-21 20:42 ` David Woodhouse
2025-08-21 20:48 ` Sean Christopherson
2025-08-21 21:10 ` David Woodhouse
2025-08-22 1:57 ` Colin Percival
[not found] ` <01000198cf7ec03e-dfc78632-42ee-480b-8b51-3446fbb555d1-000000@email.amazonses.com>
2025-08-26 19:30 ` Sean Christopherson
2025-08-27 9:30 ` David Woodhouse
2025-08-28 23:40 ` Sean Christopherson
2025-08-29 9:50 ` David Woodhouse
2025-08-29 11:08 ` Durrant, Paul
2025-08-29 11:19 ` David Woodhouse
2025-08-29 20:36 ` Sean Christopherson
2025-09-02 8:31 ` David Woodhouse
2025-09-02 17:49 ` Sean Christopherson
2025-09-02 18:23 ` David Woodhouse
2025-09-04 11:59 ` Sean Christopherson
2025-09-04 12:14 ` David Woodhouse [this message]
2025-09-04 13:25 ` Sean Christopherson
2025-09-04 13:51 ` David Woodhouse
2025-09-05 7:57 ` Sean Christopherson
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