From nobody Sun Nov 2 18:46:51 2025 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 3EB381BEF8C for ; Thu, 27 Feb 2025 02:19:14 +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=1740622756; cv=none; b=H7S3ZlFVI1SSYw5JZQG0v897NgPJ0sI8zbJNYQXRujr9C/F9a2GrIq8Ne4787Tkw/J+lLid0Bg5tg8G8rjoBeaWdZ1FgC9Vl/P8k9Lons+UCZgXhvAiSJHJuPXTvfsTk2O/mMfy+kSLi5eqaYcYE1WZkXtrs8k4rwYbhBfy0UJU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740622756; c=relaxed/simple; bh=B8tyPzR9PoDE2Pr64h/qBiff7qyIpoEROZEEit/hX78=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=r59Umboe7DF8W2p4C3E0nWmQP7B6NAoygMid+ZUfJmoZOVHEEqfNC7F+VdiL0ycYDViba7n4JBTAwtJclPPlJj9YmD/rB074DCeop/uTi4fPrBa/SB6Z14AqBwEhZrjE8nkIU+XhoLBYEJi6MLhSM2w1rUic950cgE5IDGJ92sA= 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=iiBa51h5; 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="iiBa51h5" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-223551ee0a3so1554205ad.1 for ; Wed, 26 Feb 2025 18:19:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1740622753; x=1741227553; 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=yramOYZYSvDmgSz8M8zEvByRhd31043Cze2FYqM0HuQ=; b=iiBa51h5gdzIrwfoODSWA2+hBs49NG43uvNXctmg/pM+le/SDpdXfSjNL+8wHp3E0C RVkNsxQJFyyo8GIQd9qQd+xYM27m4Wl/3gEuW0EGVgfwbox+nkSlTAmbPOGfmT7nL42F 1yat36p0E+mz7yuD+kBrdNDwmZG3pN8Y5xdkEDDyM1lJyZBKniA93uGUW03lUIRbrmvm knVtipFF+8jkLdAk2uGtgqJeVNXjOup1FxgYQ2nQrdgSWXTO5lHalAMHrF8K2rYQSwVX KP2J1Wzd2L+GFCmjQIgYcIaR4PeTQ30gkpuJUvU1sd5fcDfxk374FOK4nH81sIo8lfF5 BpHg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740622753; x=1741227553; 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=yramOYZYSvDmgSz8M8zEvByRhd31043Cze2FYqM0HuQ=; b=u5Pgyda/onDTq8at7qPneuSSKqkp2MLm8xs2sNYT561XDA1bHR5jzucwMNTIcwdDqc /7Rjoj+8Y6TJjqk8OiUI6ozrABCVOhw2THhbUVRhUaXjUmRlBlN2rCPrqHfmWbD9/N41 bRNSX53crmZOv7yDeGdvh2+R0wa2Pm3R17cKI5XRJjIvibq9gHpYhhh7lXp7jyPp/u+k TOBSNth80fXaJEmnc8Q7kiYkdJv+1OgVgL3sWtycayyPNaH08NkgwAdC1a3aNDM7Hs2O cTmDkpm05XNVp0nlh3WgH7OhwPV+IUuGeGa+RCchMFDpr3n5zWSHfdMFswfnAllCX9TI l6EA== X-Gm-Message-State: AOJu0YwaZpmGyAO0SYXsTSFbF8cwiP80rhmYeYDDOTSKmtMrUXreZK/Y wBFWurIc+rY8QAGu3ba7whWGGBfvayygsHnlspYh6uBWJs5wF251vuKBgPpRqd4+vKVB1E35XGj H8w== X-Google-Smtp-Source: AGHT+IEj/1REcONxv6g8r36LvNpCxOj7lRlC5Gm8UGTSETJJJpMqJ2Q+yEo6DBGNGx6TMjORq5yBRC/aLmE= X-Received: from pfbf4.prod.google.com ([2002:a05:6a00:ad84:b0:730:94db:d304]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:dacc:b0:220:d6ac:b5a3 with SMTP id d9443c01a7336-22320214b94mr83920905ad.51.1740622753535; Wed, 26 Feb 2025 18:19:13 -0800 (PST) Reply-To: Sean Christopherson Date: Wed, 26 Feb 2025 18:18:22 -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: <20250227021855.3257188-7-seanjc@google.com> Subject: [PATCH v2 06/38] x86/tdx: Override PV calibration routines with CPUID-based calibration 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 TDX guest, explicitly override the TSC frequency calibration routine with CPUID-based calibration instead of potentially relying on a hypervisor-controlled PV routine. For TDX guests, CPUID.0x15 is always emulated by the TDX-Module, i.e. the information from CPUID is more trustworthy than the information provided by the hypervisor. To maintain backwards compatibility with TDX guest kernels that use native calibration, and because it's the least awful option, retain native_calibrate_tsc()'s stuffing of the local APIC bus period using the core crystal frequency. While it's entirely possible for the hypervisor to emulate the APIC timer at a different frequency than the core crystal frequency, the commonly accepted interpretation of Intel's SDM is that APIC timer runs at the core crystal frequency when that latter is enumerated via CPUID: 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). If the hypervisor is malicious and deliberately runs the APIC timer at the wrong frequency, nothing would stop the hypervisor from modifying the frequency at any time, i.e. attempting to manually calibrate the frequency out of paranoia would be futile. Deliberately leave the CPU frequency calibration routine as is, since the TDX-Module doesn't provide any guarantees with respect to CPUID.0x16. Opportunistically add a comment explaining that CoCo TSC initialization needs to come after hypervisor specific initialization. Cc: Kirill A. Shutemov Signed-off-by: Sean Christopherson --- arch/x86/coco/tdx/tdx.c | 30 +++++++++++++++++++++++++++--- arch/x86/include/asm/tdx.h | 2 ++ arch/x86/kernel/tsc.c | 8 ++++++++ 3 files changed, 37 insertions(+), 3 deletions(-) diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index 32809a06dab4..42cdaa98dc5e 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -8,6 +8,7 @@ #include #include #include +#include #include #include #include @@ -1063,9 +1064,6 @@ void __init tdx_early_init(void) =20 setup_force_cpu_cap(X86_FEATURE_TDX_GUEST); =20 - /* TSC is the only reliable clock in TDX guest */ - setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE); - cc_vendor =3D CC_VENDOR_INTEL; =20 /* Configure the TD */ @@ -1122,3 +1120,29 @@ void __init tdx_early_init(void) =20 tdx_announce(); } + +static unsigned long tdx_get_tsc_khz(void) +{ + struct cpuid_tsc_info info; + + if (WARN_ON_ONCE(cpuid_get_tsc_freq(&info))) + return 0; + + lapic_timer_period =3D info.crystal_khz * 1000 / HZ; + + return info.tsc_khz; +} + +void __init tdx_tsc_init(void) +{ + /* TSC is the only reliable clock in TDX guest */ + setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE); + setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); + + /* + * Override the PV calibration routines (if set) with more trustworthy + * CPUID-based calibration. The TDX module emulates CPUID, whereas any + * PV information is provided by the hypervisor. + */ + tsc_register_calibration_routines(tdx_get_tsc_khz, NULL); +} diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h index b4b16dafd55e..621fbdd101e2 100644 --- a/arch/x86/include/asm/tdx.h +++ b/arch/x86/include/asm/tdx.h @@ -53,6 +53,7 @@ struct ve_info { #ifdef CONFIG_INTEL_TDX_GUEST =20 void __init tdx_early_init(void); +void __init tdx_tsc_init(void); =20 void tdx_get_ve_info(struct ve_info *ve); =20 @@ -72,6 +73,7 @@ void __init tdx_dump_td_ctls(u64 td_ctls); #else =20 static inline void tdx_early_init(void) { }; +static inline void tdx_tsc_init(void) { } static inline void tdx_safe_halt(void) { }; =20 static inline bool tdx_early_handle_ve(struct pt_regs *regs) { return fals= e; } diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 6a011cd1ff94..472d6c71d3a5 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -32,6 +32,7 @@ #include #include #include +#include =20 unsigned int __read_mostly cpu_khz; /* TSC clocks / usec, not used here */ EXPORT_SYMBOL(cpu_khz); @@ -1563,8 +1564,15 @@ void __init tsc_early_init(void) if (is_early_uv_system()) return; =20 + /* + * Do CoCo specific "secure" TSC initialization *after* hypervisor + * platform initialization so that the secure variant can override the + * hypervisor's PV calibration routine with a more trusted method. + */ if (cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC)) snp_secure_tsc_init(); + else if (boot_cpu_has(X86_FEATURE_TDX_GUEST)) + tdx_tsc_init(); =20 if (!determine_cpu_tsc_frequencies(true)) return; --=20 2.48.1.711.g2feabab25a-goog