From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (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 8D52D400161 for ; Fri, 15 May 2026 19:21:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778872878; cv=none; b=f7tnNG+XtSVBqm5UDnrjschk9N6+1z23hL8EJfCB+bB/jHmwJhMfLcItiIr2PSJFi0Dt2pUxx/CZxcGL3SfcMDzBAYLNPVu0hfV1kOQiACLtIhEAIzvVe/a/UzdnG9alMFJ59a+gYxEMKo3eiXmOZuuHmpcLJJWm6TVOSheL2+U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778872878; c=relaxed/simple; bh=lj0Wrx3Iv//hmkaQGmo4E+9Pr8EcmWhtdqcjCm5wSw8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=TAc4fIpYbDIlzazp+2DO/rUTsTBuyho+GwTZEMNE52Q08cOFJwbjRcdrEYWIKYChNqVlWrsCouAekKc5eHtyhdZNoyCJroZw/scRRCxI0bnFxWwKuSn1GmpqXsDAiNpJSv57MFjVuU2pF06kPQgfFgUoCeOiQVfOIeE10XKnP/0= 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=K9Dkyqfa; arc=none smtp.client-ip=209.85.215.202 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="K9Dkyqfa" Received: by mail-pg1-f202.google.com with SMTP id 41be03b00d2f7-c799ee56bd6so145593a12.2 for ; Fri, 15 May 2026 12:21:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1778872876; x=1779477676; darn=vger.kernel.org; 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=b8iwHk13SynGR+feSoAEVsPbJ8RDfXFvMc9oOLx500A=; b=K9Dkyqfa3RaGeSD8dV91pA0SluiqNnvEpIfy8bSrL8dt07s42DBDdTxdF8TWIJXBZ0 gd7uoOe9IaaJ1oxipmVXSa8wQmP1hW8zl/lpvvdz6y9f2Zf7tA+BcWonVW4l4hfG2DoF 6sBiKuz4kD1/k7mklFm+uPAhuBLm8Q88Dkp+khpqdm6EuHIHkR4lYew+9B/fpdJVOt9p V5Lf/Eo8q0WaexeC7VsKg2DcpWHkgteLymlZi1hGe1kkCZ9QcXUVHp9saVG+bq8TDAGc eAXx6InNtl9Au705LR8nUacjdCNUIe45Z1IoIdm3g3knnopCaWpJLtv86/W2/fxrc46X pwvw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778872876; x=1779477676; 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=b8iwHk13SynGR+feSoAEVsPbJ8RDfXFvMc9oOLx500A=; b=O8/ehVM5WGWs17Gv4jtW0Y7AhKSH53O27xS9DRpAmClTu0YQpztKF2wOy1+WANSoHL 68mDRMJPA4VG4/3B8bG7AMpHH1fOOMvrOZs5yzM7x8xgY+MU3RZhDCeAU6HkuJ1HLUHx Crvi+d575Rt6O8XPdLU13jL6LkAb+LCAuBpwgJrjTKz2UjfOHhLQgWHawl67Pfah30af N/wtTUxOqfnSfKmjHnSLj0WwN9KecZGr9+AzeuPSTfVAo0SSdjnCeSGtTTNWB5cIh5Y2 KnEgDsv5+Bv8r8iyKVkw0kW4FF497YGkCbhqpVvpLnR9Qq5M9dGgVU0FQ5p0twp/Msvp HYWw== X-Forwarded-Encrypted: i=1; AFNElJ8VRziMYRK5SZ8rnd5/C7C/N8jdS1iHa57sAkULoSgkMzWJsVNTnRMV5K5oo+8dAGu3XCbE27ilxhNcTKw=@vger.kernel.org X-Gm-Message-State: AOJu0YxjcD2GsPDCCCHWZfObmLEIpe3PRSI04WUaxXDCuaIADq9BuR+r UO3Z13lqFxb2O5QjGEvwVMdAlMnU4A5vILjsxNyGJoxXsDRT3btV+uT4cVwuhn3pfqiYd+dQwTV CmSiFvA== X-Received: from pfmm20.prod.google.com ([2002:a05:6a00:2494:b0:835:43a4:4aaa]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:4293:b0:835:41f3:f440 with SMTP id d2e1a72fcca58-83f33bf68e4mr5394751b3a.14.1778872875569; Fri, 15 May 2026 12:21:15 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 15 May 2026 12:19:37 -0700 In-Reply-To: <20260515191942.1892718-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org 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: <20260515191942.1892718-37-seanjc@google.com> Subject: [PATCH v3 36/41] x86/kvmclock: Get local APIC bus frequency from PV CPUID Timing Info 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" When running as a KVM guest with kvmclock support enabled, stuff the APIC timer period/frequency with the local APIC bus frequency reported in CPUID.0x40000010.EBX instead of trying to calibrate/guess the frequency. See Documentation/virt/kvm/x86/cpuid.rst for details. Signed-off-by: Sean Christopherson --- arch/x86/include/asm/kvm_para.h | 1 + arch/x86/kernel/kvm.c | 19 ++++++++++++++++--- arch/x86/kernel/kvmclock.c | 13 +++++++++++-- 3 files changed, 28 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h index 3f7f558b5b24..381d029b72e7 100644 --- a/arch/x86/include/asm/kvm_para.h +++ b/arch/x86/include/asm/kvm_para.h @@ -130,6 +130,7 @@ void kvmclock_init(void); void kvmclock_cpu_action(enum kvm_guest_cpu_action action); bool kvm_para_available(void); unsigned int kvm_para_tsc_khz(void); +unsigned int kvm_para_apic_bus_khz(void); unsigned int kvm_arch_para_features(void); unsigned int kvm_arch_para_hints(void); void kvm_async_pf_task_wait_schedule(u32 token); diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 5cd92a0b156a..bfe36e361b3c 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -918,12 +918,25 @@ bool kvm_para_available(void) } EXPORT_SYMBOL_GPL(kvm_para_available); -unsigned int kvm_para_tsc_khz(void) +static bool kvm_cpuid_has_timing_info(void) { u32 base = kvm_cpuid_base(); - if (cpuid_eax(base) >= (base | KVM_CPUID_TIMING_INFO)) - return cpuid_eax(base | KVM_CPUID_TIMING_INFO); + return cpuid_eax(base) >= (base | KVM_CPUID_TIMING_INFO); +} + +unsigned int kvm_para_tsc_khz(void) +{ + if (kvm_cpuid_has_timing_info()) + return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_TIMING_INFO); + + return 0; +} + +unsigned int kvm_para_apic_bus_khz(void) +{ + if (kvm_cpuid_has_timing_info()) + return cpuid_ebx(kvm_cpuid_base() | KVM_CPUID_TIMING_INFO); return 0; } diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index 5ceba4f3836c..abcc5b36ea1d 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -200,10 +200,19 @@ void kvmclock_cpu_action(enum kvm_guest_cpu_action action) */ static unsigned long kvm_get_tsc_khz(void) { +#ifdef CONFIG_X86_LOCAL_APIC + u32 apic_khz = kvm_para_apic_bus_khz(); + /* - * If KVM advertises the frequency directly in CPUID, use that - * instead of reverse-calculating it from the KVM clock data. + * Use the TSC frequency from KVM's (and other hypervisors') PV CPUID + * leaf when available, instead of reverse-calculating it from the KVM + * clock data. As a bonus, the CPUID leaf also includes the local APIC + * bus/timer frequency. */ + if (apic_khz) + lapic_timer_period = apic_khz; +#endif + return kvm_para_tsc_khz() ? : pvclock_tsc_khz(this_cpu_pvti()); } -- 2.54.0.563.g4f69b47b94-goog