From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A22BB40340F for ; Fri, 15 May 2026 19:21:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778872889; cv=none; b=P3Fl0zMhglFO6rNlJ1Xu/iXuHpiXC7v3sp/X9zMVRU8A1yIhzbYiasO8PkTQHLlzUypz466t3pMTM4J28KmOR5RdXSE1jf5GdNv84GEXMsjV5QXSGjEN7IoeNNBfnBadwMQ6PU5Qq7OCYoGUqYMlMdsDmnzKUBGBv+UWAQZ3Yig= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778872889; c=relaxed/simple; bh=QioBrwKpRdsCytYFTzNNbiVitx8MQJE4M4sQvpXgFXY=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=EsO92Uc+EPVRVKIXmbGtQXoTiuFe1nJ8wSwLxlLQQQihca5FEQuudFaBJCKOcL9XEtoDnzamjTIuE8/DEexi9We8f3KKSPLmztaff5Sn71uWLoAoqpv00HMg95QVmIiz/yy/lEpp+2VKsAa/v1br5MkSWswohjHrvv4aGfxrOBc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=cBnxmMln; arc=none smtp.client-ip=209.85.215.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="cBnxmMln" Received: by mail-pg1-f201.google.com with SMTP id 41be03b00d2f7-c829586e894so69904a12.2 for ; Fri, 15 May 2026 12:21:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1778872885; x=1779477685; darn=lists.linux.dev; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=5BJQi7ZR1svDe2KF7RHkPrmL6MBNA7Dkc8gFvThdUD0=; b=cBnxmMlnSczUfCvjJ4IK0it6gclw0HudADy8FxyLeawlGnFu0WTD0rweIcI9/ewOF8 P7iOwpXLvm0IkKLDNMz2IS/3yj6+MjaenaRgMmglgC0Rx6u35JPrnMHpJkhQooXtvIR+ ToGCJOm+MkE0i/zEVzPQJ3MTtnS6p4/TzKRoVItQTROQouNfN9Jd+r2UB3D1dPEafuYA gIPIbLdleqTqWNNPZHJUCyq7GtD+td0C+zGNry32vfmbHgQk2K70+ThwQ2AEB1vlVkMQ E3akH8Rtm2mMWTMYJ9bHobA3SQV/A1vTUOJnj/ptj3rM8YHdUJD79eiuvymp937IKWQ0 s2Xg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778872885; x=1779477685; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=5BJQi7ZR1svDe2KF7RHkPrmL6MBNA7Dkc8gFvThdUD0=; b=JgMIy/hkkpRoYraX17T7QTnJMPi2bqG/wOveVzVmUHKegDditccxRlcUIoQGXymeRv vXmB6lxoD4Km9DIZBW+A1SKB9+vyXxLtMvFjtmklUBOsMdYreknEefX6IEVwRX+SRZ+z pItXxBz0wviDvVaon7ja3z/BCd2bltN+UCoHrZd9dGduyWVZffKM42FqhxS/CGwvr0PV zKusWcOhVECMNszFxmKlZPkme0dC4B+8/3jGLKta0s/zMtiElM9dpYN0PBpwMTJcOpdL eSQkIBPjSyYSx+Oz93UmR/mToO4FelQ/8+WQUR1xgmIKcI+X2IXpHu4efbONPDyeLNf0 roAw== X-Forwarded-Encrypted: i=1; AFNElJ8yaA4tss+UV3+zdnYlvxJYnHjsHN2Xa4cWkIlm12ZNTKJeTRaAwrqZCy8ksGz+HVYxvxzfSb0Pf+Cz@lists.linux.dev X-Gm-Message-State: AOJu0YwUmXd/nffciqf96P6au1/A3Fi9ANfa6uc7LfvuXzk3iY1R5hT1 rRFlbT5TxxIj/LxSJPypN5++mbZwTBO8SsKfA42IF3s9bWgxe3A+FmcXXU98wCBI5AIW730Hbgi egEdBrQ== X-Received: from pfbeq4.prod.google.com ([2002:a05:6a00:37c4:b0:82f:344e:386a]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:9502:b0:838:1c02:2763 with SMTP id d2e1a72fcca58-83f33ab667bmr5736284b3a.9.1778872884225; Fri, 15 May 2026 12:21:24 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 15 May 2026 12:19:42 -0700 In-Reply-To: <20260515191942.1892718-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260515191942.1892718-1-seanjc@google.com> X-Mailer: git-send-email 2.54.0.563.g4f69b47b94-goog Message-ID: <20260515191942.1892718-42-seanjc@google.com> Subject: [PATCH v3 41/41] x86/kvmclock: Get CPU base frequency from CPUID when it's available From: Sean Christopherson To: Kiryl Shutsemau , Paolo Bonzini , Sean Christopherson , "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 Content-Type: text/plain; charset="UTF-8" If CPUID.0x16 is present and valid, use the CPU frequency provided by CPUID instead of assuming that the virtual CPU runs at the same frequency as TSC and/or kvmclock. Back before constant TSCs were a thing, treating the TSC and CPU frequencies as one and the same was somewhat reasonable, but now it's nonsensical, especially if the hypervisor explicitly enumerates the CPU frequency. Signed-off-by: Sean Christopherson --- arch/x86/kernel/kvmclock.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index 62c8ea2e6769..7607920ae386 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -190,6 +190,20 @@ void kvmclock_cpu_action(enum kvm_guest_cpu_action action) } } +static unsigned long kvm_get_cpu_khz(void) +{ + unsigned int cpu_khz; + + /* + * Prefer CPUID over kvmclock when possible, as the base CPU frequency + * isn't necessarily the same as the kvmlock "TSC" frequency. + */ + if (!cpuid_get_cpu_freq(&cpu_khz)) + return cpu_khz; + + return pvclock_tsc_khz(this_cpu_pvti()); +} + /* * If we don't do that, there is the possibility that the guest * will calibrate under heavy load - thus, getting a lower lpj - @@ -434,7 +448,7 @@ void __init kvmclock_init(void) kvm_sched_clock_init(stable); } - tsc_register_calibration_routines(kvm_get_tsc_khz, kvm_get_tsc_khz, + tsc_register_calibration_routines(kvm_get_tsc_khz, kvm_get_cpu_khz, tsc_properties); x86_platform.get_wallclock = kvm_get_wallclock; -- 2.54.0.563.g4f69b47b94-goog