From mboxrd@z Thu Jan 1 00:00:00 1970 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 692CA4DD6EB for ; Wed, 1 Jul 2026 19:32:50 +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=1782934372; cv=none; b=Sq1Up80vPf1SUO/QjKnO0gzQTqir+nEo3e6cNAvCOgcURMwQEAGBDJNvKmt97fURE0Ok2jo03Oc5H6mTsAGqMq+DcJNP+Nxro6phUC/xbFadOhTwm9HVqKF2BVyJCeNSRt3QUlP5xUKGK1ByWt/U0r0PBcwqJD/nqkxYgBpJF18= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782934372; c=relaxed/simple; bh=BNbYGSH55jffEq4VtE+b969iyJXTMV1HTMSCzkA3sgE=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=puR3zsDN+dgEccu0vQ/a/vMoqtuUgpCON2zWw4K9yMYtoveLo0iostY/d1bnGSU/loHe9g45VgUs/rLeDQNHte1CQ4fdYjjVjcMfsZsa5r+87ZW7seTK9wfK7t7s4rEXlR3Gl5ypF9PKlXeu/wUNqiO+1X4rvsLHfJAmfm+Oc54= 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=bzSY0zfV; 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="bzSY0zfV" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-2ca3b314193so12002965ad.1 for ; Wed, 01 Jul 2026 12:32:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1782934370; x=1783539170; 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=/Hl8ESM1aN3u3Me6yWngcHpVlzQnDyaS4TqcnFx8YJ8=; b=bzSY0zfV3sQISOLEXSMU9Rx+LaG7hgWOWuH9eD/j7Y6W2CWaYmQZoPO8EKrcaXttvq pDZlvC18OrMwrFpHQPoD/UwNqo/QdoUVlw5+ufy/WujzdTn8jZq0asEB4fAXGf4ncekk NWR6ABCslXLJ6aNRnEGVbS7UVNFZNrkv35/2eA/aGR9FeIDzz2xnYH0anm2UOnILKGdb FWKOlsPm33iHyNZGqPCsGu8YI4o9ezLRE2/+9XUM+F0nlks1ovwQNnbhx8rRUSaRNstX xyynBX4Sbm342TanQgv2IA04LPU53tVzCDYFGHPj8sFrYyfYd89wFAczHvefjrg/kwR5 8CtQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782934370; x=1783539170; 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=/Hl8ESM1aN3u3Me6yWngcHpVlzQnDyaS4TqcnFx8YJ8=; b=YiB5xtQQCKjD5pYpl+TNyBdLAYZDNpngumgfGaBVTtxkDjIKJkJd7ruQ3sbM2fk1sI HntGEjRIYWETtwjqzTdFIaUt/PtZVBzkmI+5VEW6SAaz8TbOkqgtj3eGtbC6VXslraVL wukCYFVNsYbHYyjgv/T/fddEWaKEY8oEO1qJeGAXO3khiz8Xag8u85zg2AVFh36+tNrF 9Cs+1EHzPoCA3s4qjFGkNgZkoD75E2S7LG7FIQpo2bL1bIGLc5WZ0TLkS8tOOKSNtJK8 lKO53lEHLZUXS6rqToD5+6waclM2LLsGug6k//L1E05TJE+PHEbOjVbW+qMqZfuUtEHL 3qNw== X-Forwarded-Encrypted: i=1; AHgh+RrEc8RMFTwh/MDwf6oiLGiMNYL9n3Qzvmg3P251qzuqUhwfNqYlB6+GUs+ZXK6GXhg7/KUQDrJPkGhA98M=@vger.kernel.org X-Gm-Message-State: AOJu0YyMItjUVaV4k/8wu7rRJjZzov6tI772VBKxsna/ciCl4XpPDWHx lHOP1kZjL0D4O6hCOwqwy9Iuvc4X7gVkZdck0Kzi0b9TTJMUoo4wkFTeg6xF6NMXFDqZAJUY12w 7Qs6OXQ== X-Received: from plrx15.prod.google.com ([2002:a17:902:b40f:b0:2c0:bd65:1a98]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:18e:b0:2c9:e86e:a9f5 with SMTP id d9443c01a7336-2ca7e73cbd7mr31240015ad.18.1782934369266; Wed, 01 Jul 2026 12:32:49 -0700 (PDT) Reply-To: Sean Christopherson Date: Wed, 1 Jul 2026 12:31:40 -0700 In-Reply-To: <20260701193212.749551-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260701193212.749551-1-seanjc@google.com> X-Mailer: git-send-email 2.55.0.rc0.799.gd6f94ed593-goog Message-ID: <20260701193212.749551-20-seanjc@google.com> Subject: [PATCH v5 19/51] x86/kvmclock: Drop dead check on TSC being unstable during kvmclock_init() From: Sean Christopherson To: Jonathan Corbet , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Kiryl Shutsemau , Rick Edgecombe , 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: Shuah Khan , "H. Peter Anvin" , Vitaly Kuznetsov , Broadcom internal kernel review list , Boris Ostrovsky , Stephen Boyd , linux-doc@vger.kernel.org, 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, Tom Lendacky , Nikunj A Dadhania , David Woodhouse , David Woodhouse , Michael Kelley , Thomas Gleixner Content-Type: text/plain; charset="UTF-8" As pointed out by Sashiko[*], kvmclock_init() runs before __setup() and thus before notsc_setup() or tsc_setup() can mark the TSC unstable. kvmclock_init() also runs well before tsc_init(), and even before tsc_early_init(). Simply delete the check, as it's been dead code since it was introduced. Note, odds are good the check_tsc_unstable() call was copied from Xen's xen_time_init()+xen_tsc_safe_clocksource() logic (as so much of KVM's PV code was). However, xen_time_init() runs via x86_init.timers.timer_init(), which is invoke from x86_late_time_init(), and thus after params have been parsed. Alternatively, kvmclock could register itself later on, or tsc_setup() could be parsed as an early param. Given that there's zero evidence there was any meaningful intent or need to actually check for an unstable TSC, go with the simplest option. Fixes: 7539b174aef4 ("x86: kvmguest: use TSC clocksource if invariant TSC is exposed") Link: https://lore.kernel.org/all/20260529181213.0B27A1F00893@smtp.kernel.org [*] Signed-off-by: Sean Christopherson --- arch/x86/kernel/kvmclock.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index 061a22d31dea..29ca37e9a3bc 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -362,8 +362,7 @@ void __init kvmclock_init(void) * */ if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && - boot_cpu_has(X86_FEATURE_NONSTOP_TSC) && - !check_tsc_unstable()) + boot_cpu_has(X86_FEATURE_NONSTOP_TSC)) kvm_clock.rating = 299; clocksource_register_hz(&kvm_clock, NSEC_PER_SEC); -- 2.55.0.rc0.799.gd6f94ed593-goog