From nobody Tue Aug 25 23:56:34 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 6AD4E4DD6F1 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=SsDNpI7uRUzs/1DaySdrh5aFWYGwuSk/dDAz5FrdsyBflcnHEDNC0tttXKbYDROvl2hhouIqtqZ8fwgEY/dOk8Jfb6MPL5gS/Wt39EfVR6oCVrFghIPAqf3Ji1UgzHruOE5THawvbRSmytQf1QS5CdrMXScedPauXrmBAdAGtk0= 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=LvuK7Ikb; 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="LvuK7Ikb" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-2c9960cf96cso12691005ad.3 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=1782934369; x=1783539169; 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=LvuK7Ikbgf3c+eZq/cpmdlcqUpa+qLo1f3a0ZbvQCww2amiuagU95Q/WpBMvANfY3I YLbdK2VaW8cIHkrmBdNFLzPc4lSZVlimmU4QZ/0ASvMOa12DpvTV0yA8pt2dYXHnK2pb 7a7lcLkLpQuB+xPfTq2T/gQxqJJsSZMmpuMUzOq3/bzQjtIYW8cbgE8qGsqz4zJoB6ea my9IIu1/B2+dtSW8hP/XWToFNFZIeqbgRAksZvFsGrbEsLBIdpvRRDZGqnpOx9q/rOA/ C58ftKujaU0tKdi/I7R6wL+bFF9WrFll8E8XvxiRNQ2h9rCsTZRIWnA3W/gngxCkfYVT gmxw== 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=rhz66Z/qtTkH4bfsvg6he5Gmmpb31qA25KdnZri+lLmw6fKNo0VXOlmHWizmeFUQv9 2YHqULM0cs7WThSSNl7sAvepN3YdPGtvMtwsOb5LgdUHvAbd1klFRgAI2mrGb9oeZFAc 2jPQVASgGj9UN5m9XjkcGxkNkcHsSZvR9SjrjsmTcM8Jz6PDhKDc10wJYcOEoEvLNb8x dZDuXobwpWSxiNBZjaqnriVQCotUC6wJpiFw8tLs/6Ny51Q8l4NWOk3Hb7bh2pOq68dy 6JGoWrgAucQHCeQNr4RQxM29GARxqLfNahnTdwavEreB1wd2D7E2jT9KT1dQFmOne/vu MO4Q== X-Forwarded-Encrypted: i=1; AHgh+RropCUQ58h3hSvqYn++Tpd6ythr75emOfv4vWdnqvUKL4bzZKbxSzL3w59oS71ATdxxAeGpbgavwgDjzUc=@vger.kernel.org X-Gm-Message-State: AOJu0Yy0O0lSD4uxESr4tDNfmonkD/Gtt8oHdhx8P5/7JLQlf4g9qegg nqkvu1aw1lSx/fmSQfAEdIt7qGrvGNXo32pX3F9dlzyl6SkCIQre3Rd1Y8WJ3qqDONC9fK0h8lQ bP8lzQg== 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-kernel@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-Transfer-Encoding: quoted-printable 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 i= s exposed") Link: https://lore.kernel.org/all/20260529181213.0B27A1F00893@smtp.kernel.o= rg [*] 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 =3D 299; =20 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC); --=20 2.55.0.rc0.799.gd6f94ed593-goog