From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (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 32C2E3EFFA1 for ; Fri, 29 May 2026 14:44:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780065898; cv=none; b=Rd99711l2+WFhJ6vShDE83Q+GE0gasZz3TnkP+igKOIX4pOopAtWCUByMlLQOHXQpmVjIg1+uwvlDLSamAWlGB58Xuj6YYpo0aWORhhmSiL0/XqOPLK3ih6fxDcybCkGDivmXV6aTZybGgPbI6qXvk6FcrzTK2G1pmN+v1ryTFA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780065898; c=relaxed/simple; bh=l/nBAPcX2JVrvTnp5qYOh0JGDYFqeR/54KQDU8KHwXI=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=WWip6SoMBA1UAQicwwByOUeOpNwBg0qKT9KvrRbRaY79ezEqwR2Zuui+NrCc+vPv6Aa+5KRoYrplnP14ZDBbwhaqHt6vgVrLhYZ/HK5rvTgvUuCZ4Y819NE/dpdBO/z2xqGKi828OYi+FsoI1QbHMlcnPM0CoOf2OeDH5oeOmi4= 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=wZwJ4diG; arc=none smtp.client-ip=209.85.216.74 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="wZwJ4diG" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-36b982ec338so1811701a91.0 for ; Fri, 29 May 2026 07:44:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1780065896; x=1780670696; 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=Q/Ssx6Evg+apl0YO4v5bDvJ7vmmhU3NWEJgFIU1d/78=; b=wZwJ4diGV/k3mKwvauiGChangZ3ruYgkHjtPp7aKZP6ImWSRZqV8MGpc9FadELyoYQ tyepKB+L3yY0hm6ZS5Rndk9QxNV8aRY1TNQo4c7DbDhsrebJnBfy/NYwA0Ha/rTjyzAu DZiTLTC5Qfuv2zQMAkyHdL9sF16WYA9sP6u2cSE/xoQH25oXnpf1rWsEtVN6mTQFIvRM FjJTwXObxoraA0MDuJ1Zwb9rNdV14VlMaBUWmnoLnTuPwcMPTOo1aWUretlYX1cK+DEf G100qGqBNNVQq14C5Z7lKLoJtYuTmARhAICahjZ23x0B9l0yWXxsj6kJOdl0cEtd/Sbo zCVw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1780065896; x=1780670696; 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=Q/Ssx6Evg+apl0YO4v5bDvJ7vmmhU3NWEJgFIU1d/78=; b=a4H6X1KXyGWKSK4HnaXb7jwl9oKP+tmV2CLh9zOaQqDKmIpHyqtoPKEzHT3skcdYQy QuBoUs2N1NfpHdzCM1PFML9k5LcAVU0hYGwkqjn1+FjkavcF0ra7Cbj3LyZUv+QYPUAX 5E9o/ruqsFHawtNXJCbWmswR2CHC0wl9UwvGsObu+6MFqpSKQMs8VJIxIxSb0FUPRxDA X6mxkAw2LXta0USh6lqMJJrP/hmkI0EPa5KE/BhzSY4BcEkTR1xOkJ1TGnU6UF6Sba03 mAhlWLZwsVtJ34XoCytAZzDMYUzpWurBIRrcbhOn0sd+qtdDFrBIzKNXQ8Kc6hzkR1Ng cMTg== X-Forwarded-Encrypted: i=1; AFNElJ+EvNGNHQQNHrb1sqk7ffxhr2e/d0rMFzhfZWPOKs4/CABkHBPDtRb/aQSQDUL4vFhRjPKAjhFq7FsP@lists.linux.dev X-Gm-Message-State: AOJu0YyMkoA9G59iEXuMnRIueYMqhfSxanyXBu4iGkknMIFE+HKTTEnP 7lg2hDVrD6JoP73N7IDx+4DmPmzHMmknyAiiojqVKetk26Hx8c7+uOR+T+NBFXioRmXVqhEtSiV nKH1yEA== X-Received: from pjnu11.prod.google.com ([2002:a17:90a:890b:b0:36b:8d3f:d136]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:1dd1:b0:368:ac5f:d31b with SMTP id 98e67ed59e1d1-36bbd006f90mr3628748a91.24.1780065896168; Fri, 29 May 2026 07:44:56 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 29 May 2026 07:43:51 -0700 In-Reply-To: <20260529144435.704127-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260529144435.704127-1-seanjc@google.com> X-Mailer: git-send-email 2.54.0.823.g6e5bcc1fc9-goog Message-ID: <20260529144435.704127-5-seanjc@google.com> Subject: [PATCH v4 04/47] x86/sev: Don't override CPU frequency calibration for SNP's Secure TSC 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" Don't override the kernel's CPU frequency calibration routine when registering SNP's Secure TSC calibration routine. SNP (the architecture) provides zero guarantees that the CPU runs at the same frequency as the TSC. The justification for clobbering the CPU routine was: Since the difference between CPU base and TSC frequency does not apply in this case, the same callback is being used. but that's simply not true. E.g. if APERF/MPERF is exposed to the VM, then the CPU frequency absolutely does matter. While relying on heuristics and/or the untrusted hypervisor to provide the CPU frequency isn't ideal, it's at least not outright wrong. Fixes: 73bbf3b0fbba ("x86/tsc: Init the TSC for Secure TSC guests") Cc: Nikunj A Dadhania Cc: Tom Lendacky Signed-off-by: Sean Christopherson --- arch/x86/coco/sev/core.c | 1 - 1 file changed, 1 deletion(-) diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c index ed0ac52a765e..665de1aea0ee 100644 --- a/arch/x86/coco/sev/core.c +++ b/arch/x86/coco/sev/core.c @@ -2046,7 +2046,6 @@ void __init snp_secure_tsc_init(void) snp_tsc_freq_khz = SNP_SCALE_TSC_FREQ(tsc_freq_mhz * 1000, secrets->tsc_factor); - x86_platform.calibrate_cpu = securetsc_get_tsc_khz; x86_platform.calibrate_tsc = securetsc_get_tsc_khz; early_memunmap(mem, PAGE_SIZE); -- 2.54.0.823.g6e5bcc1fc9-goog