From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (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 6C56E3FD96E for ; Fri, 29 May 2026 14:45:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780065916; cv=none; b=lSxoTbHnqvLhETfXhf/fZs+H/q2KEKqra8zwWwyUWD/zeIxKjDcQcJ7B7NsT1jsJoxRMtce2uyQtJavutumsGOO1vQ9kQ168NdGfyxEcsvXBtomhf/F0TUw9A6rH/VZthI8OUt9xM+Pc9RXQ88W3knjp9rhYvCd0eUB534Xi+tw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780065916; c=relaxed/simple; bh=UUytjfT9SVOtFZ9usAuTuI+mwQ/wQQjELPCBSRuUOk4=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=GApwJLijxsBAw2xiOdiW0x25QqHp5lhw7Fb9KfH6CoWZAV+Yz+P7JeG32BehkD4OauVOHLRTzEmpaCpjzKnFRIVgbD4LVpmIqGgcXjPT855RL1LTKEUZmNczXHDK3zxVhB6ChTpsJSV2BJZidm/062M1tBKI3sKLTFF8sBIX/pU= 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=iCpF4V/x; arc=none smtp.client-ip=209.85.214.202 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="iCpF4V/x" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-2bc763c7256so290876395ad.3 for ; Fri, 29 May 2026 07:45:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1780065914; x=1780670714; 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=Xkng2ObvqyeOAHFFD1k5jEREhKyPX3M1bjFdIhQCaZo=; b=iCpF4V/xS5L0CFm1qHNNHZwnKS6VtCDsbO/RHMZ8YtoccNuNMMOPzh2J8WcPMjgvyJ Y4GQpx6hyof7WijKJ5VV0qeUJWD2OOKA114Zmnp9lj+enYGrVuoZ2SVRLGAPgcRTQX0U y1EOYx2337M0INVoXhOMN8AaveqlnZ/e3WUC8jIjpEPzVwfkiFckTdQI5nKaGx2uSLoq FzEKZTMjChRvb476h4al7lO9t57KLSH7mdg4ueNGe6xFN0ttOcBoFPpRzdBMF6/Zeff2 EVOm8goRREj09Im9RSQUp4ka78wZCQbqLxSzTC0+vkpXhsS2CupMlGjd4HmgjPsCJmcu BUJg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1780065914; x=1780670714; 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=Xkng2ObvqyeOAHFFD1k5jEREhKyPX3M1bjFdIhQCaZo=; b=mkRqYge1W9W3rMZQ1vQHeT6doxVxyITYbsvuxjLxZPsAh3c/mzZUYAlbwWazAUNqnD 1khLR5nphw8xEH5RV+bs9drU9mF170XKntAewWpkec75yP21B34/IhvToPeN6htbzV4z 6IvEgucNmhjxAuukQ9DoyTYdPJ2IXP4RgbAf6XFGmmApFMSFgigUyAq8NHhLO95m1K6r QQJ92cS33EiemKTri7OTUnmXoEUe1+2aPldbR1K9fMA65koOr7+H4wXw1e+Z9k9woimt x6cGVuF47YHtJ5RrIskUOZ2fTn/JasPdE8BTp8GsN+SSs3NAI8rtrVbWj90BmRKs6BUy JAiA== X-Forwarded-Encrypted: i=1; AFNElJ+/BMc5JOMDrU3iv1fESl5mAgkaQa3J5WxYuyFL3gY4XPxKXD8cdbPqzu+6kijNoe/yIangaQ4S04Xvf0w=@vger.kernel.org X-Gm-Message-State: AOJu0YwpY8y2SoPgTcrUmU63fBwIEOxkA0xIFZhztonXs2/b/W4udPS6 5PiDdOn425wM8u1DVwxFh2QAmsFFpoVBJpFTulAg2VgQyBcL9AifxedbyshfPAMGfSflyXovIOG VgTPptw== X-Received: from plhl2.prod.google.com ([2002:a17:903:1202:b0:2b0:5b0d:f4db]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:1508:b0:2bc:b141:8551 with SMTP id d9443c01a7336-2bf36833ef4mr1185145ad.19.1780065913278; Fri, 29 May 2026 07:45:13 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 29 May 2026 07:44:05 -0700 In-Reply-To: <20260529144435.704127-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260529144435.704127-1-seanjc@google.com> X-Mailer: git-send-email 2.54.0.823.g6e5bcc1fc9-goog Message-ID: <20260529144435.704127-19-seanjc@google.com> Subject: [PATCH v4 18/47] x86/kvm: Get local APIC bus frequency from PV CPUID Timing Info From: Sean Christopherson To: Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Kiryl Shutsemau , Sean Christopherson , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Ajay Kaher , Alexey Makhalov , Jan Kiszka , Andy Lutomirski , Peter Zijlstra , Juergen Gross , Daniel Lezcano , John Stultz Cc: "H. Peter Anvin" , Rick Edgecombe , Vitaly Kuznetsov , Broadcom internal kernel review list , Boris Ostrovsky , Stephen Boyd , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, linux-hyperv@vger.kernel.org, virtualization@lists.linux.dev, xen-devel@lists.xenproject.org, David Woodhouse , Tom Lendacky , Nikunj A Dadhania , David Woodhouse , Michael Kelley , Thomas Gleixner Content-Type: text/plain; charset="UTF-8" When running as a KVM guest with PV timing info provided by the host, 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. Note, the unit of measurement for lapic_timer_period is "ticks per HZ", not Khz. See Documentation/virt/kvm/x86/cpuid.rst for details. Signed-off-by: Sean Christopherson --- arch/x86/kernel/kvm.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 4fe9c69bf40b..c1139182121d 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -977,6 +977,7 @@ static void __init kvm_init_platform(void) .mask_lo = (u32)(~(SZ_4G - tolud - 1)) | MTRR_PHYSMASK_V, .mask_hi = (BIT_ULL(boot_cpu_data.x86_phys_bits) - 1) >> 32, }; + u32 apic_khz __maybe_unused; u32 timing_info_leaf; bool tsc_is_reliable; @@ -1039,6 +1040,13 @@ static void __init kvm_init_platform(void) x86_init.hyper.get_tsc_khz = kvm_get_tsc_khz; x86_init.hyper.get_cpu_khz = kvm_get_tsc_khz; } + +#ifdef CONFIG_X86_LOCAL_APIC + /* The leaf also includes the local APIC bus/timer frequency.*/ + apic_khz = cpuid_ebx(timing_info_leaf); + if (apic_khz) + lapic_timer_period = apic_khz * 1000 / HZ; +#endif } /* -- 2.54.0.823.g6e5bcc1fc9-goog