From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 50B76380FC5 for ; Sat, 16 May 2026 07:42:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778917366; cv=none; b=mqhO/g4FMG/FT82+ZocsvgpCW3Ta3KybSHefa0EtmguWFCyTwcpb3bz5W4F0MbtBDDKkVWQd6leCZJi70LQeEaA9SojmAa1y4iTod3ZI4rLB/5vG7a/VLE+SgpH2Vy3nSPBblG0IvaAo8oQIAS7aoK18uqn3NpxbzhUVz9VAHew= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778917366; c=relaxed/simple; bh=fjfgd+v14zGBl7L8xu1eqInSO4/HBRf2Tumh7X99mpM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=aCX/gd+jUNRlN9mAwgsvUuq9KhZ23H7BBA24sczFJs9lOYq0RR/T/mmo5hUfcJMKPy8Reps+F7l0DBkwvoxiFq7SSsZrhkBbazC6mrEZygU8JF4IeaF4Un8vrz06rR48Z+pS3fhB2N4X6ndqabqLZaXRBeJmZHv8qLVjgEp3VBg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=XMkEzLfk; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="XMkEzLfk" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1778917364; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=ZuYuwk7J/15Ge1PYKnSZO6EKNDeWPqqx6skfRaS0DUA=; b=XMkEzLfkNCt/fjt4YrhIdzEgioCcz5eQ/GYTHKGO4fy/QGLbcXNe/IhbaqKlXjm38/1DHH rrrJKUsk59gAZTeukqXOt69AaONRtcScQBVoFPHAONN94XmUJWgjEgB7pBG+4mMf3gxcaH IAKCWRHgAtnESWrt9fsrsl3q8MMHejs= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-111-C2qozkjxOF6c4Hglw-NMVQ-1; Sat, 16 May 2026 03:42:38 -0400 X-MC-Unique: C2qozkjxOF6c4Hglw-NMVQ-1 X-Mimecast-MFC-AGG-ID: C2qozkjxOF6c4Hglw-NMVQ_1778917355 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 39F2518005B2; Sat, 16 May 2026 07:42:34 +0000 (UTC) Received: from [10.44.32.24] (unknown [10.44.32.24]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 0353F180034E; Sat, 16 May 2026 07:42:22 +0000 (UTC) Message-ID: <3cb683b4-973a-4b3e-a5d5-a8baa8a70eb0@redhat.com> Date: Sat, 16 May 2026 09:42:19 +0200 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 40/41] x86/tsc: Add standalone helper for getting CPU frequency from CPUID To: Sean Christopherson , Kiryl Shutsemau , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Ajay Kaher , Alexey Makhalov , Jan Kiszka , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Juergen Gross , Daniel Lezcano , Thomas Gleixner , John Stultz Cc: Rick Edgecombe , Vitaly Kuznetsov , Broadcom internal kernel review list , Boris Ostrovsky , Stephen Boyd , x86@kernel.org, linux-coco@lists.linux.dev, kvm@vger.kernel.org, linux-hyperv@vger.kernel.org, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, Michael Kelley , Tom Lendacky , Nikunj A Dadhania , Thomas Gleixner , David Woodhouse References: <20260515191942.1892718-1-seanjc@google.com> <20260515191942.1892718-41-seanjc@google.com> From: Paolo Bonzini Autocrypt: addr=pbonzini@redhat.com; keydata= xsEhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2 CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04 hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAc0j UGFvbG8gQm9uemluaSA8cGJvbnppbmlAcmVkaGF0LmNvbT7CwU0EEwECACMFAlRCcBICGwMH CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRB+FRAMzTZpsbceDp9IIN6BIA0Ol7MoB15E 11kRz/ewzryFY54tQlMnd4xxfH8MTQ/mm9I482YoSwPMdcWFAKnUX6Yo30tbLiNB8hzaHeRj jx12K+ptqYbg+cevgOtbLAlL9kNgLLcsGqC2829jBCUTVeMSZDrzS97ole/YEez2qFpPnTV0 VrRWClWVfYh+JfzpXmgyhbkuwUxNFk421s4Ajp3d8nPPFUGgBG5HOxzkAm7xb1cjAuJ+oi/K CHfkuN+fLZl/u3E/fw7vvOESApLU5o0icVXeakfSz0LsygEnekDbxPnE5af/9FEkXJD5EoYG SEahaEtgNrR4qsyxyAGYgZlS70vkSSYJ+iT2rrwEiDlo31MzRo6Ba2FfHBSJ7lcYdPT7bbk9 AO3hlNMhNdUhoQv7M5HsnqZ6unvSHOKmReNaS9egAGdRN0/GPDWr9wroyJ65ZNQsHl9nXBqE AukZNr5oJO5vxrYiAuuTSd6UI/xFkjtkzltG3mw5ao2bBpk/V/YuePrJsnPFHG7NhizrxttB nTuOSCMo45pfHQ+XYd5K1+Cv/NzZFNWscm5htJ0HznY+oOsZvHTyGz3v91pn51dkRYN0otqr bQ4tlFFuVjArBZcapSIe6NV8C4cEiSTOwE0EVEJx7gEIAMeHcVzuv2bp9HlWDp6+RkZe+vtl KwAHplb/WH59j2wyG8V6i33+6MlSSJMOFnYUCCL77bucx9uImI5nX24PIlqT+zasVEEVGSRF m8dgkcJDB7Tps0IkNrUi4yof3B3shR+vMY3i3Ip0e41zKx0CvlAhMOo6otaHmcxr35sWq1Jk tLkbn3wG+fPQCVudJJECvVQ//UAthSSEklA50QtD2sBkmQ14ZryEyTHQ+E42K3j2IUmOLriF dNr9NvE1QGmGyIcbw2NIVEBOK/GWxkS5+dmxM2iD4Jdaf2nSn3jlHjEXoPwpMs0KZsgdU0pP JQzMUMwmB1wM8JxovFlPYrhNT9MAEQEAAcLBMwQYAQIACQUCVEJx7gIbDAAKCRB+FRAMzTZp sadRDqCctLmYICZu4GSnie4lKXl+HqlLanpVMOoFNnWs9oRP47MbE2wv8OaYh5pNR9VVgyhD OG0AU7oidG36OeUlrFDTfnPYYSF/mPCxHttosyt8O5kabxnIPv2URuAxDByz+iVbL+RjKaGM GDph56ZTswlx75nZVtIukqzLAQ5fa8OALSGum0cFi4ptZUOhDNz1onz61klD6z3MODi0sBZN Aj6guB2L/+2ZwElZEeRBERRd/uommlYuToAXfNRdUwrwl9gRMiA0WSyTb190zneRRDfpSK5d usXnM/O+kr3Dm+Ui+UioPf6wgbn3T0o6I5BhVhs4h4hWmIW7iNhPjX1iybXfmb1gAFfjtHfL xRUr64svXpyfJMScIQtBAm0ihWPltXkyITA92ngCmPdHa6M1hMh4RDX+Jf1fiWubzp1voAg0 JBrdmNZSQDz0iKmSrx8xkoXYfA3bgtFN8WJH2xgFL28XnqY4M6dLhJwV3z08tPSRqYFm4NMP dRsn0/7oymhneL8RthIvjDDQ5ktUjMe8LtHr70OZE/TT88qvEdhiIVUogHdo4qBrk41+gGQh b906Dudw5YhTJFU3nC6bbF2nrLlB4C/XSiH76ZvqzV0Z/cAMBo5NF/w= In-Reply-To: <20260515191942.1892718-41-seanjc@google.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Mimecast-MFC-PROC-ID: fCeyMSUcJ5tdBRWMtMe7Z62xb5fSM5pfOVHbDUpU8z4_1778917355 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 5/15/26 21:19, Sean Christopherson wrote: > Extract the guts of cpu_khz_from_cpuid() to a standalone helper that > doesn't restrict the usage to Intel CPUs. This will allow sharing the > core logic with kvmclock, as (a) CPUID.0x16 may be enumerated alongside > kvmclock, and (b) KVM generally doesn't restrict CPUID based on vendor. Even for native there's no real reason to restrict to Intel, I think. native_calibrate_tsc() only limits itself because historically (prior to commit 604dc9170f24, "x86/tsc: Use CPUID.0x16 to calculate missing crystal frequency", 2019-05-09) it used a hardcoded table of crystal frequencies. Of course paranoia applies, but for virtualization, if the leaf exists there is no reason not to trust it. Thanks, Paolo > No functional change intended. > > Signed-off-by: Sean Christopherson > --- > arch/x86/include/asm/tsc.h | 1 + > arch/x86/kernel/tsc.c | 37 +++++++++++++++++++++++-------------- > 2 files changed, 24 insertions(+), 14 deletions(-) > > diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h > index f458be688512..c145f5707b52 100644 > --- a/arch/x86/include/asm/tsc.h > +++ b/arch/x86/include/asm/tsc.h > @@ -91,6 +91,7 @@ struct cpuid_tsc_info { > }; > extern int cpuid_get_tsc_info(struct cpuid_tsc_info *info); > extern int cpuid_get_tsc_freq(struct cpuid_tsc_info *info); > +extern int cpuid_get_cpu_freq(unsigned int *cpu_khz); > > extern void tsc_early_init(void); > extern void tsc_init(void); > diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c > index 1b569954ae5e..745fa2052c74 100644 > --- a/arch/x86/kernel/tsc.c > +++ b/arch/x86/kernel/tsc.c > @@ -719,6 +719,24 @@ int cpuid_get_tsc_freq(struct cpuid_tsc_info *info) > return 0; > } > > +int cpuid_get_cpu_freq(unsigned int *cpu_khz) > +{ > + unsigned int eax_base_mhz, ebx, ecx, edx; > + > + *cpu_khz = 0; > + > + if (boot_cpu_data.cpuid_level < CPUID_LEAF_FREQ) > + return -ENOENT; > + > + cpuid(CPUID_LEAF_FREQ, &eax_base_mhz, &ebx, &ecx, &edx); > + > + if (!eax_base_mhz) > + return -ENOENT; > + > + *cpu_khz = eax_base_mhz * 1000; > + return 0; > +} > + > /** > * native_calibrate_tsc - determine TSC frequency > * Determine TSC frequency via CPUID, else return 0. > @@ -754,13 +772,8 @@ unsigned long native_calibrate_tsc(void) > * clock, but we can easily calculate it to a high degree of accuracy > * by considering the crystal ratio and the CPU speed. > */ > - if (!info.crystal_khz && boot_cpu_data.cpuid_level >= CPUID_LEAF_FREQ) { > - unsigned int eax_base_mhz, ebx, ecx, edx; > - > - cpuid(CPUID_LEAF_FREQ, &eax_base_mhz, &ebx, &ecx, &edx); > - info.crystal_khz = eax_base_mhz * 1000 * > - info.denominator / info.numerator; > - } > + if (!info.crystal_khz && !cpuid_get_cpu_freq(&cpu_khz)) > + info.crystal_khz = cpu_khz * info.denominator / info.numerator; > > if (!info.crystal_khz) > return 0; > @@ -787,19 +800,15 @@ unsigned long native_calibrate_tsc(void) > > static unsigned long cpu_khz_from_cpuid(void) > { > - unsigned int eax_base_mhz, ebx_max_mhz, ecx_bus_mhz, edx; > + unsigned int cpu_khz; > > if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) > return 0; > > - if (boot_cpu_data.cpuid_level < CPUID_LEAF_FREQ) > + if (cpuid_get_cpu_freq(&cpu_khz)) > return 0; > > - eax_base_mhz = ebx_max_mhz = ecx_bus_mhz = edx = 0; > - > - cpuid(CPUID_LEAF_FREQ, &eax_base_mhz, &ebx_max_mhz, &ecx_bus_mhz, &edx); > - > - return eax_base_mhz * 1000; > + return cpu_khz; > } > > /*