From nobody Mon Feb 9 14:38:35 2026 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (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 8C61723BF9A for ; Thu, 27 Feb 2025 02:20:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740622808; cv=none; b=X0ukGJGL/w5HTxnxUqypDWuxqsXSw+i1D00OKRwTKMwcd4XdhiQx3ASpU+Wl2VFZqXieYoFZqj0lD0dH/SWvc9pzYDim5Xi59Bm0Le547gnv3hegLKJlXQRX/5hm22fKMFD8fDgUYh2TlZ8hclV4eAfuIG3riNtGhVUgwtG5tBw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740622808; c=relaxed/simple; bh=KkUJ82b9H7sinf/zXMFW+qV85JdkMspMIEMKpj9sh/I=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=j8ZPesKIydY6xi+eSPJH92+RoETJB57tv2APukses1O9mZOOa9eGvwGqdJ1P7o8xte7BPemyt101a0AI3ON2vujCsiPlAoVJlznRMc43gmFZK+3WWpUuaa7i10Wkf/hLjnDxoyuSRAzosfmBIsPQtqVvlhuLpy5bTNCdq4Z+cAI= 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=xDWDxp79; arc=none smtp.client-ip=209.85.214.201 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="xDWDxp79" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-220ee2e7746so7721775ad.2 for ; Wed, 26 Feb 2025 18:20:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1740622805; x=1741227605; darn=vger.kernel.org; h=content-transfer-encoding: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=pIteN/a7AZFre1KWgiuGeMT9S5HjiwYxYNebWBQLyrA=; b=xDWDxp79/1M3lU1GI0eNK0+ov4M4OQhhtamiQ2b5jpTvZt57VQVra8dae2Cq/IkdNu HldMFBMhLlBUsb7IsKR0lkNGVts9WVZT442m6HhowMFMIFPRZz/Y+zhoIDyJbWNPeG7E ssOTG8b83s48PlRX7a4JVDZCAsejjhW4sG1PHRqy80BFX1E4Wqc+Xuunr2/fNaCjJNYF CGzYEvzo2TQi483h25AE98d5KqQJE/LkSfbN/mcxL3XOr1fA0Hf96d4DBs2i0myXUQGu UQJN4ByTXK00xz7Ybmd11NvuwYT/HEgbZOrRVZzrpOdSPgaqd7r7+YIkl6+aWHh4M8YP 68mA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740622805; x=1741227605; h=content-transfer-encoding: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=pIteN/a7AZFre1KWgiuGeMT9S5HjiwYxYNebWBQLyrA=; b=I06VAr5OlzGT+YDSPIJy2yE/P2INd3RIgecfgXe+NMKH8clhSy7qDFFfAI+JHyEcnb ufDHnOizriB5Kusxq3d9LDUXOJIP26jNyAWetiLsl79oaD8Ve8grXjTaXEtVw8SJ27SV Cl1xeSaw4uPN6q10MpoaoLL+jzuVMxQpoEPdw7YrZK8VKNi7yfQi6VYc4gxCbrDv7nrP +NFODfRf6hoAZVZl9GOrpoEU9NHoDOaQ7zCD5UxmxYWImQcckSDBVgSExr0O5aTePyFv V3Qd3s+RmLoCgcoi6CyPH1VdUju+i60fl0sjNvz5MOUT283/GIXQhmolL4S94OZ9mMlq 1TaA== X-Gm-Message-State: AOJu0YzfV+/sH6M4kcNtBxynOw+dvxlDzQSusLxvPaWJ1UB0XG6rGYxX BL39mM6tUe2OmW/wxYBib+neJP8rFqqenlf13Qkn2fcMXr4iy8kQXkwMdqVRj9FIzFbzAalIJOj QWw== X-Google-Smtp-Source: AGHT+IGP2cZX6cw4gCRMv2fLrFe/TXNI5NPzTOobUK44ADJodiEA9LQbSXwMRfyGc0rCQ4WOggdSpeUhPyc= X-Received: from pfhk13.prod.google.com ([2002:aa7:998d:0:b0:730:479d:3482]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:2181:b0:731:ff1b:dd6a with SMTP id d2e1a72fcca58-7348be4c455mr8342588b3a.20.1740622805598; Wed, 26 Feb 2025 18:20:05 -0800 (PST) Reply-To: Sean Christopherson Date: Wed, 26 Feb 2025 18:18:52 -0800 In-Reply-To: <20250227021855.3257188-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250227021855.3257188-1-seanjc@google.com> X-Mailer: git-send-email 2.48.1.711.g2feabab25a-goog Message-ID: <20250227021855.3257188-37-seanjc@google.com> Subject: [PATCH v2 36/38] x86/kvmclock: Stuff local APIC bus period when core crystal freq comes from CPUID From: Sean Christopherson To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "Kirill A. Shutemov" , Paolo Bonzini , Sean Christopherson , Juergen Gross , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Ajay Kaher , Jan Kiszka , Andy Lutomirski , Peter Zijlstra , Daniel Lezcano , John Stultz Cc: linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, kvm@vger.kernel.org, virtualization@lists.linux.dev, linux-hyperv@vger.kernel.org, xen-devel@lists.xenproject.org, Tom Lendacky , Nikunj A Dadhania Content-Transfer-Encoding: quoted-printable 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 core crystal frequency from CPUID.0x15 (if CPUID.0x15 is provided). KVM's ABI adheres to Intel's SDM, which states that the APIC timer runs at the core crystal frequency when said frequency is enumerated via CPUID.0x15. The APIC timer frequency will be the processor=E2=80=99s bus clock or core crystal clock frequency (when TSC/core crystal clock ratio is enumerated in CPUID leaf 0x15). Signed-off-by: Sean Christopherson --- arch/x86/kernel/kvmclock.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index 3efb837c7406..80d9c86e0671 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -192,8 +192,18 @@ static unsigned long kvm_get_tsc_khz(void) { struct cpuid_tsc_info info; =20 - if (!cpuid_get_tsc_freq(&info)) + /* + * Prefer CPUID over kvmclock when possible, as CPUID also includes the + * core crystal frequency, i.e. the APIC timer frequency. When the core + * crystal frequency is enumerated in CPUID.0x15, KVM's ABI is that the + * (virtual) APIC BUS runs at the same frequency. + */ + if (!cpuid_get_tsc_freq(&info)) { +#ifdef CONFIG_X86_LOCAL_APIC + lapic_timer_period =3D info.crystal_khz * 1000 / HZ; +#endif return info.tsc_khz; + } =20 return pvclock_tsc_khz(this_cpu_pvti()); } --=20 2.48.1.711.g2feabab25a-goog