From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (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 027A43FDC16 for ; Fri, 29 May 2026 15:08:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780067296; cv=none; b=Ur5OXRB80kz/s2lhIeL1Um6wPtwkSftkE0o0XDUlVeSNovifZbMNYnj2sDTGjNHkyOgvnleE/RYbCYf5N3Tmh6Zk3QiT1hh9Vd9Um+TEaTSDIOu0sshzEPJXhbTQmFQjw25cRo5r5JAwyxGBuQT+xEMErgqYh0vK2K2FPZWadGc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780067296; c=relaxed/simple; bh=BSjCZV2prw1SrJXvAtpxbttBG+ZHRGmcDc0NH0Lv54Q=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=a4v7Q37sRplVhbgyPtMKUyMiE7ONWgOurZbgozUau6xXyvPzlPuV3SwGNKlTgQjMfhNx02kGLBU2+1wld8hbvZjLayubDXaE6izJFLK4LNpA9M6MoRLtwaYu+PSclbPiPiP4pN64m5Syvnc0gr3bdAz81DxLb7rKiYTaFijJ/WE= 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=HWsQQpIX; arc=none smtp.client-ip=209.85.214.202 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="HWsQQpIX" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-2b2ecc96a9aso160818615ad.1 for ; Fri, 29 May 2026 08:08:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1780067294; x=1780672094; 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=IXSUk0zrc0SOIpzpc8N9Re3bKO3sQJVctQ52bfDdTtc=; b=HWsQQpIXibrW7pLkwpweCcE9YYwxWaJbQd7GD5mPSkiQ/oDb00JtMpR3wS9abueVuy wh4qOZ2KTLWHfCcDNVUI6q527xOU+ntPUnMou+QUjayJd4CoMqbyNNKzQ1GE45pJwx1b UCwmVpZorH3UOdKBABFU18CVPFmQRfVh07dQc4PUrWxgRjCuspvo079JAlSuu4P49fpD 2czKXAUvHRmJlb7w1bKQwbkY4JJvD8VvhxxPjaIH0x16ptx7wG+Gj+BuLhD+DSEidbah nggOLVC4lT825dwrRD91QvXs7cF6c1zEzemmdaFxhbdTnX2GkLKsq7mlvQJJ3Q92sTU9 +Ezg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1780067294; x=1780672094; 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=IXSUk0zrc0SOIpzpc8N9Re3bKO3sQJVctQ52bfDdTtc=; b=snpaw/TfErNUsDtZjHiybAXjiT5X8+l1aHkRDzHmhUztzGXGTRe1Lo6crW5oVum92E sMW8IVKSvLRLk8qjKZOFUVPuECkPITlxzJmLGkFuvsc4y9x6y4V1SZl8lfgYa0/nA/gm wtmEcClJM7KpReUP0iTQS6o4nUSSb0mWxTa5OnzTEUIiZbb1oV2WlNUKxpMZIgUxjZ7B 8QFI6iM/s4ljNaWhFSSiQVPmqbJ9H1nkNSj/4tccZBw5DraBjQsaAJlaHAgLCJfmaIsY lHbgccLAzLibpST5s9moY9L9WjXnACj3EEXUE6kLz/GBAu8SK7eXAmjAr+VKp+kPkqlo 8QuQ== X-Forwarded-Encrypted: i=1; AFNElJ957X1XdvN/ex8uoRnzhlBdPHZ5aOMAfQQCYmaoJjnrCn2ser6yHs/pmgdfCJ0ndoFAICq+Yuyuzga9pFs=@vger.kernel.org X-Gm-Message-State: AOJu0YxCh7B+uqhiLiFGhx7q1f3cVIr+DfEt5C0Ap8nn41A9kXMQ8lx4 iIaINdEMp7v4AeRSZEluMTaOIOsmhMbuCP6pJw0z6qk/VNfHNhb/U5t4pKE47P0EJEU0GeyqB84 xZuXH4Q== X-Received: from plblh4.prod.google.com ([2002:a17:903:2904:b0:2ae:ceb3:f968]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:e842:b0:2ba:6ebe:4897 with SMTP id d9443c01a7336-2bf367b37demr2834085ad.3.1780067294027; Fri, 29 May 2026 08:08:14 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 29 May 2026 08:08:12 -0700 In-Reply-To: <20260529144435.704127-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260529144435.704127-1-seanjc@google.com> X-Mailer: git-send-email 2.54.0.823.g6e5bcc1fc9-goog Message-ID: <20260529150812.714604-1-seanjc@google.com> Subject: [PATCH v4 38/47] x86/kvmclock: Refactor handling of PVCLOCK_TSC_STABLE_BIT during kvmclock_init() From: Sean Christopherson To: Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Kiryl Shutsemau , 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: "H . Peter Anvin" , Rick Edgecombe , Vitaly Kuznetsov , Broadcom internal kernel review list , Boris Ostrovsky , Stephen Boyd , 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, David Woodhouse , Tom Lendacky , Nikunj A Dadhania , 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 6372b4dc7b0c..4e304f1c887d 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -305,7 +305,7 @@ 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; @@ -332,11 +332,18 @@ 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; -- 2.54.0.823.g6e5bcc1fc9-goog