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 D1F9622D4D0 for ; Thu, 27 Feb 2025 02:19:43 +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=1740622786; cv=none; b=a5zaDJK4+ykJE1y9dZv4/AUDYrezhq0fuu9cqzCk4V2i12wjPfrSHkK9c8YNXUDyFcRu3cYCOlb3n5mcjzk2jCvqDzn37w7X/7ziu6xDUlBy02QuSCEu+0iToDTLUa6ybWOJ3NIHU/oegaudLhBPmoDWAuTFdHKE1syt2w4VIt4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740622786; c=relaxed/simple; bh=c8XZYUiY0W1+X8puZluFjrjS+RyDGH52gngoWNRH5Ko=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=F77VVFoRrBdjoCSgJPH/cUOWlTk74pxMP9qnCecmQW5OdQxKGxo0YFxRyvqkKj1+FlknklauQEXChMs+Q+bomkB4+fyPB+1EkcZUhb8lQQPBzrRNsN6SNnOzKPFhQEp021fGBEOnqd7zr6LXd5e0PzSNFauk71RpPX6KVYOQIcA= 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=ukCcfPyB; 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="ukCcfPyB" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-2fc1eabf4f7so1109589a91.1 for ; Wed, 26 Feb 2025 18:19:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1740622783; x=1741227583; 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=Za0nk5QeJovZveNmDgTJSzh3R0hb/7p0/gaKYZ4C/Vs=; b=ukCcfPyB2dChFiuU0mGQNxIy9Zg363Osg3ycP2MhCCcGvSZqQwtjv259Gz70nMsDQA HSgDzw5AhNeVThOQwaXL3JANsBTFmyGMGGmpeAnRonui+1Yw9mRsECTgNyIYyxa63exi 5AnBQnguu1QhLnhGngeCOxUIKvkiF35UZ06wTZDcMl4/AbFZbwxrfmo9sCQjsKRh0PLd 5gw3HRGDrZ8lJY4XT1vdVE8Vbac6kFhSzR6hJP0B3VblurT88HeUj4nnIaOkUDW41hop 7nvQCkxHmwwtkUeBljDP/ka7FEO3A4+tA4xdk+ZjHXcD0bnYUdS8rnzHVmSJIaFx5iVu zQcA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740622783; x=1741227583; 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=Za0nk5QeJovZveNmDgTJSzh3R0hb/7p0/gaKYZ4C/Vs=; b=mVe3cWmI6eQwWe1DZ4VrBfI5GYvKBMlK/IAKSXTP2yBxfryLku4zmJduzEx3VcWNap +jwHA+wj0AzH8kvyvBCMg3HOUzq1vbJ3gBP+tEdzIq2esmA/TyXOe2PV8hDf7M9Y/yMk JPkXtvWl3FEZa/XJuK0Xtxa0Jd9nq/lGiWh0ya3/OtJG6j45gYhknXjb7JypN6cddJJw uQ2DwDgc3GkoT0IOeMHq3zu+Mkgu1ozIASU5kq9LfW/4LEsJEweK7xJOBHXQzH79/w4d dkPxcgxguYKIPHl4+Q3stXOjdrGs1UYeI+DJdusVuVqe9X1b2rJ1zxMbY6AvPaI6f3O2 2X3w== X-Forwarded-Encrypted: i=1; AJvYcCXDxxrcXjYBhhgGF8dY0X8U7is+EYC/gP/qwKsBnv1lLVDTm4Ksa3lNOVZW951C0GplsgDqwg94seg5yVl2eA==@lists.linux.dev X-Gm-Message-State: AOJu0YxD0DQQSix3f/5jgEBbHvxbmBljUUO1NPQddBGwFG1Yg8Ps9kSO V4dyLCqML0HzZ98iTov8B2aaUSQ5bxrwMU78d0UW8TNWWD0UcK9nmuwpGi61N6Rz8QPrYTPkFkL wFQ== X-Google-Smtp-Source: AGHT+IHPEy5y9WPVcI/hX8J+CDDBk9ezIawKhLRmwSNwFlW/vj5Sb4uKTsOn6iseYydXRMp+Q/+8QjZLtQQ= X-Received: from pjbsm1.prod.google.com ([2002:a17:90b:2e41:b0:2f8:4024:b59a]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90a:d2d0:b0:2ee:b6c5:1def with SMTP id 98e67ed59e1d1-2fe68ad9ef3mr15165448a91.8.1740622783395; Wed, 26 Feb 2025 18:19:43 -0800 (PST) Reply-To: Sean Christopherson Date: Wed, 26 Feb 2025 18:18:39 -0800 In-Reply-To: <20250227021855.3257188-1-seanjc@google.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250227021855.3257188-1-seanjc@google.com> X-Mailer: git-send-email 2.48.1.711.g2feabab25a-goog Message-ID: <20250227021855.3257188-24-seanjc@google.com> Subject: [PATCH v2 23/38] x86/kvmclock: Refactor handling of PVCLOCK_TSC_STABLE_BIT during kvmclock_init() From: Sean Christopherson To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "Kirill A. Shutemov" , Paolo Bonzini , Sean Christopherson , Juergen Gross , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Ajay Kaher , Jan Kiszka , Andy Lutomirski , Peter Zijlstra , Daniel Lezcano , John Stultz Cc: linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, kvm@vger.kernel.org, virtualization@lists.linux.dev, linux-hyperv@vger.kernel.org, xen-devel@lists.xenproject.org, Tom Lendacky , Nikunj A Dadhania 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. 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 934ee4a4c6d4..0580fe1aefa0 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -304,7 +304,7 @@ static void __init kvm_sched_clock_init(bool stable) void __init kvmclock_init(void) { - u8 flags; + bool stable = false; if (!kvm_para_available() || !kvmclock) return; @@ -331,11 +331,18 @@ void __init kvmclock_init(void) 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); tsc_register_calibration_routines(kvm_get_tsc_khz, kvm_get_tsc_khz); -- 2.48.1.711.g2feabab25a-goog