From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f198.google.com (mail-pf1-f198.google.com [209.85.210.198]) (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 5E9754AB801 for ; Thu, 6 Aug 2026 23:37:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786059438; cv=none; b=o8EC5q0JUi5zMfrOMu3YKTfHT4ukrMQNgOJBLqxBDLNrula/LXgmbs79fceuN35PN2JSq+u9OmiXq+NfdgYHPsgUKX3qnX4hRF5Ag3FQWWstxwmPI1Lc0UJXkHOyP6P6XU5bVVJ77zfFX8+kyKYRr4IB01XSH5msmTNzsgD0uys= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786059438; c=relaxed/simple; bh=EetB+RnX28VKy0jN0zLsMSRc1BZr5Co2JodEFYoMux8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=kw7wJFjyNpnJq2WdkTO5sH37+hZ+WD4ICDilgDDAtJiRjruDC9sr8F9oVSVzcenLBFPMQYy0TdMycYJUlHoWeq/5nyiHwcDqr9QkD1hMyY6qRI5aLUwXbEevrADCKs5N6te0PFOHDFIfAioPkfYg77DzT3IdcTwZnMfpsv5L0yw= 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=BqqbRfW6; arc=none smtp.client-ip=209.85.210.198 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="BqqbRfW6" Received: by mail-pf1-f198.google.com with SMTP id d2e1a72fcca58-848860def2cso3141811b3a.2 for ; Thu, 06 Aug 2026 16:37:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1786059436; x=1786664236; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:reply-to:from:to:cc:subject:date:message-id :reply-to:content-type; bh=DfVsK4/eNAzlqgTkif/k+3bkJqkVsqeG8riFv7GGWx4=; b=BqqbRfW6nxSQG3cymW7yNa0PeYowBginEK9NyhpXgnO8/hBtGpearvWMlln3PHtTHw 8ZybP9jwoy9y5dLzZq7+/7ZwVV6nshgJsuEasoADRnQlH6CRDbs0Mhhq5LeFDH1IRMsj uFSLMnTRtwZ/XVf+0TnojBpg369/7KehsGkbQOJHKFYSvROuvCx6mnihIiOjqTUHrmyV qLOf+ajHjnFBiPrQZRZGIlbKK89KF7y+XFkjeu8oURSzLtb+P4jDznCNNrdcqPQnll6k C4OGzyRP5hAPCPJxvXjqodarzWpYON5QEsOLWATF1zzwHHgrdXKEQNWHHVB+7KJZdjOL FLyw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786059436; x=1786664236; h=content-type: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:content-type; bh=DfVsK4/eNAzlqgTkif/k+3bkJqkVsqeG8riFv7GGWx4=; b=DHyg9BURmtEqGa1hZed0o7YmoWpSgFg21BCkqjg79DJ06qKGAoHu5QsCiq7bIobVwB CZfhcqtVZk4mwsVtvkSc0g9Hd17WD8MTLiWmHMwWC2QX4klseK5UWFObdudch2bkA66G anNzgXjvWSXQ4YdIWZZJQYn25kJrItJOP9v2wuZCMHnb8ZhPthhwcykVlI0WEqUGWg+t fLjh0mr1RUoD0cJC4styaUG9NSV8wq8FenzZvS4YqUcF7e1DlUymph7s3FQh7o1yAagE fPej3iDssrnJ2lN5FTEXUlbD0OTnZ78ylyEjw+zzM2x2mcd/bfvcoXvEapOEa1cOkiHM dz1Q== X-Forwarded-Encrypted: i=1; AHgh+RoCYuXNkyC8GmgEcWNNpxAnvOhgYpk3VIFQPaJcIcHXue7ylvVI8Cl+tcLf7sa5OaypPIufOdOU9yWty3E=@vger.kernel.org X-Gm-Message-State: AOJu0Yw0p/40SD/9fdTNXzAwOcD+q5s4ymtX2tHPuWLtf89Ox5vlGRPT Bt0K6y8L1ByMPuA3Ien4TE+onbCVxBKVJPL530BZuo0yVuZq2WoNDMfdJaarcKQmwBos62EnFry JpFbTAg== X-Received: from pfbko19.prod.google.com ([2002:a05:6a00:4613:b0:847:926b:dc17]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:1886:b0:847:99a7:c751 with SMTP id d2e1a72fcca58-84f2e05d02dmr18083285b3a.25.1786059435385; Thu, 06 Aug 2026 16:37:15 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 6 Aug 2026 16:35:58 -0700 In-Reply-To: <20260806233609.212337-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260806233609.212337-1-seanjc@google.com> X-Mailer: git-send-email 2.55.0.679.g6767b8d81c-goog Message-ID: <20260806233609.212337-42-seanjc@google.com> Subject: [PATCH v6 41/51] x86/kvmclock: Refactor handling of PVCLOCK_TSC_STABLE_BIT during kvmclock_init() From: Sean Christopherson To: Kiryl Shutsemau , Rick Edgecombe , Sean Christopherson , Paolo Bonzini , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Ajay Kaher , Alexey Makhalov , Jan Kiszka , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Juergen Gross , Daniel Lezcano , Thomas Gleixner , John Stultz Cc: Vitaly Kuznetsov , Broadcom internal kernel review list , Boris Ostrovsky , Stephen Boyd , Miroslav Lichvar , x86@kernel.org, linux-coco@lists.linux.dev, kvm@vger.kernel.org, linux-hyperv@vger.kernel.org, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, Michael Kelley , Tom Lendacky , Nikunj A Dadhania , David Woodhouse , David Woodhouse , 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; -- 2.55.0.679.g6767b8d81c-goog