From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) (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 052C3429DAE for ; Wed, 1 Jul 2026 19:33:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782934400; cv=none; b=F7lPMLs6IqiwYpSiuddwThwNnnCvEivx6DfPIr41WjKCNAvIox6OTSupD3IHtmJmW9R33hshGiVwKcz4ggAw5lDsy3xulXHb3KtSxbqW4VTDH01X4hPNEW6LgfGeezNttm9CdHMYZTSgZjkPf/rWAP3diZqMy/UNTribG0uCMC8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782934400; c=relaxed/simple; bh=WFd4Q0rqoZceFAWrIK1Xzvh1py+2tI8zh2sgEj9iv78=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=UrLaRPhEAmlbEaFrPENer9mKT3/y/3zkDoVQMG6uJ96Zv4+ijPRRxUAM5yrFT4vFQUPTijC6f4LfsVuNY8Yl1PC57xH2kO2tXPlnamu3P0yGtExLkUwXiXZDdLQP4wNJBUjB76BIptiN2V+9zLpAo+L8qXIpAasl3Jrsm41gvSc= 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=hKg5bAkl; arc=none smtp.client-ip=209.85.216.73 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="hKg5bAkl" Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-37fe90ee192so1185620a91.3 for ; Wed, 01 Jul 2026 12:33:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1782934397; x=1783539197; 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=UQI87jJDSOF5xYM7+FYJ7P3rXlAyaoExltyOrt00Pyo=; b=hKg5bAklcge/JwT+f8awNmiMreptjcKgs7P5EcOYf83EBMKW/fXVo9YX8gpXEc7PZb AKFL/m4B8G5CXJJMAwOiDCWkynvG0ashzX2JpU6lLgCe/7rtFEgdzeRGR8myV0zrAYGo isANjEYlpgSp8mXn6NaBGSJ1USqzFKtqAZtgsjKXz5j5hfYEb2q6rV1Eg+iKOQvicgdb Ems0EjsEF+cnSkVGUg2t1B5w13JvfFA8Yd+ljfACXLNOgjGlGDY7NDGLZwBqJrvSHdf2 +LSR0UmrtFXxfwf+0mUbmZJk3itW8bT4YsexCuQMEs1N67vpIGElbN50pSnL4oUJrlIW qgfg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782934397; x=1783539197; 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=UQI87jJDSOF5xYM7+FYJ7P3rXlAyaoExltyOrt00Pyo=; b=D2rx98NTTy7ikETd5uXf/KzBV6trS3i85jcbSW9+kANnPl36QnBfOxTyMylJ+IDlRk 7EMMQL8QSrgo38zblmld0cC8TuL+mrZTJhiqqiGpB+hsE/MV1Bqge6ANAjrcgmAGcEl1 Cs017ORWloltLykrLe1E2/bTIS0Nvg9Ee+U6IoNwE15dqST6QcY+cSaDBy3qrEquNgLX 3/HLTWK99C+F29GV3Fq+zcfngeAwFo+6orL9VvAWPl4XN7ftLlEm8euBpEjUyivJo+z8 Ecen0qp7M/oC0S/TqOK4P3v8v0ysow+aNRhD2YQ3dpsGXchZhIXFVUKbU7Q+6i+ZWiRr Bn7A== X-Forwarded-Encrypted: i=1; AHgh+RoVqS0xmiiwVN+6ZsF37vrHThPQChxRAhkgZiGMMyjIsHNe/6oCwJV4min8PyRf56JrJrdvWStGVije+Hg=@vger.kernel.org X-Gm-Message-State: AOJu0YyxTCxu+JFI/htwLdCAQtEZRUGmfbmmR9OdL3/DRaAQ2V2VdbE6 K5yHfLWS+K0l/Mk6RYmcxkkR26Q5MC7nNWT+O8yp4TL36gOT14liv/lgy243ZhiBiT4F3ry85Rx F+AUkKg== X-Received: from pjbcv6.prod.google.com ([2002:a17:90a:fd06:b0:37d:de2f:3ddf]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:4e84:b0:37f:eda5:5169 with SMTP id 98e67ed59e1d1-380aa127da8mr2911601a91.13.1782934396852; Wed, 01 Jul 2026 12:33:16 -0700 (PDT) Reply-To: Sean Christopherson Date: Wed, 1 Jul 2026 12:32:02 -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: <20260701193212.749551-42-seanjc@google.com> Subject: [PATCH v5 41/51] x86/kvmclock: Refactor handling of PVCLOCK_TSC_STABLE_BIT 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" Clean up the setting of PVCLOCK_TSC_STABLE_BIT during kvmclock init to make it somewhat obvious that pvclock_read_flags() must be called *after* pvclock_set_flags(). Note, in theory, a different PV clock could have set PVCLOCK_TSC_STABLE_BIT in the supported flags, i.e. reading flags only if KVM_FEATURE_CLOCKSOURCE_STABLE_BIT is set could very, very theoretically result in a change in behavior. In practice, the kernel only supports a single PV clock. Reviewed-by: David Woodhouse Signed-off-by: Sean Christopherson --- arch/x86/kernel/kvmclock.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index 5220d205abc7..61d4d943fe74 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -327,7 +327,7 @@ static __init void kvm_sched_clock_init(bool stable) void __init kvmclock_init(bool prefer_tsc) { - u8 flags; + bool stable = false; if (!kvm_para_available() || !kvmclock) return; @@ -354,11 +354,18 @@ void __init kvmclock_init(bool prefer_tsc) kvm_register_clock("primary cpu clock"); pvclock_set_pvti_cpu0_va(hv_clock_boot); - if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) + if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) { pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); - flags = pvclock_read_flags(&hv_clock_boot[0].pvti); - kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT); + /* + * Check if the clock is stable *after* marking TSC_STABLE as a + * valid flag. + */ + stable = pvclock_read_flags(&hv_clock_boot[0].pvti) & + PVCLOCK_TSC_STABLE_BIT; + } + + kvm_sched_clock_init(stable); if (!x86_init.hyper.get_tsc_khz) x86_init.hyper.get_tsc_khz = kvmclock_get_tsc_khz; -- 2.55.0.rc0.799.gd6f94ed593-goog