From mboxrd@z Thu Jan 1 00:00:00 1970 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 AD82548A2D9 for ; Fri, 15 May 2026 19:20:56 +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=1778872858; cv=none; b=L/eTRFwsKCurMsCdtEWOtKUwogDNrBc8sgn0BnOoq3XBYpKIf923Y7qtRK6GQ5UCTrENNzZhINK5kwg0F/Eg7hshL/30xVxLpdBshYFyTbFoQ+boodQnfCqVDBhAKbvyd4WtMhW08T2cf4bN0f51+5vqYkTNftuBCSu0rvwrz0M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778872858; c=relaxed/simple; bh=XHuFwpmRMigDS8aPY2gzeqSH8+iLJhWYuJEhRhC21LM=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=d6zLJyHUBu2D0IZ7X/WOvBr+kOKTjHPMV0T9JJjwRyo5zvP3xED/QZXCb++5NYccr6W/DX1iCyZLD1nU+ydzO52H3k/KBJyXgqfJ8Qq5vcDinuijFvHL8NC+uBzOXtOH4KSMDCN0kgN/nE7nsBTQTXlhjXQ3va8bfYPgSM7YUDw= 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=eUPq0DBy; 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="eUPq0DBy" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-2b99eb06178so4590535ad.2 for ; Fri, 15 May 2026 12:20:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1778872856; x=1779477656; 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=7w7qT+Z66rWfxvtZ1IzSRlO054bgZsKsszMlQ0FarYw=; b=eUPq0DBy2Ud9j1dRLabCDt13MLF7Y1kNR83HHPkU2erkmGHVP14hnocKJXUg9vi8/v EhxfwcAFHvd4pJJJqToShcEYICMSQSqs3yzNjLVwmWjfnWwXpjUtYR6ta1Wem66feVG9 T0EFqDxaN5jPYFIpEot0HuUQjxXFI6O3+IRoxWWiAfWos/hn4yIpreHhis9TprcWX9a9 6ySBJGHvdzHnJCpEMLB2rjS4rROBvBJt+kOvdRx72q/yhzvEW0PW+9HIaXBd0EmWVp3L k/L6Y9By8QQ+52KpxQrvaEED5aSz4uz2vqVzdqsNtnV79cuH5q6CUJV8xLpRxAeTT7zl LJWQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778872856; x=1779477656; 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=7w7qT+Z66rWfxvtZ1IzSRlO054bgZsKsszMlQ0FarYw=; b=Af502FWF7rcwFKjuvh0Nyd6FWABGLQy8PKCBuvvfXJfqVjzIPmB9Oa9Y/rOcsNWaTq 9CGs4HJ9o8HSN+g0XMXR/PeKP1W5jO7rj3hUeiq3NgRA2LuqpYcb5FGIeXOPP/FK7qmA X1fIdMnBQLh+v0UXuar6oZDU6bKB43SvQJeQYsD/hMze5A/ypphMBb/ceFv0kKmE5qbM PZf6jW5qxYbv+Q84yKzxluxzicLEzy0HFJFhlG4NgNnltIp33xr7YzjpzqKY991ZFew6 RzPAuAvtGyQ2Trh3rCLtifnEDaAdHt40m2KD8hFSb1GpG31vxgpCXTcs8adw7EqkURMt 6anA== X-Forwarded-Encrypted: i=1; AFNElJ8k4XQHIGZxVU70Nl0auuxYBXkSG7fqru2YjvSIuS0SMTqoV+etGO5YGiXPuXBBNQcUXwySavqhG0b0b0vnGA==@lists.linux.dev X-Gm-Message-State: AOJu0Yw1cNfc7i/IRGsxG+9EAVpbhzifLbS+ViHt8q3+pROpHHxPc1Ei 5Q5mOWMK2PefqC1OCJZk7gTGUk6xI+Wa0QXwXXDCP+tnB737hrUzitA+WoPT/m1x/8pCpISshfM BvDQ2vA== X-Received: from plcm4.prod.google.com ([2002:a17:902:f204:b0:2b0:b12e:1b07]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:ee09:b0:2b4:62bd:ee3 with SMTP id d9443c01a7336-2bd7e937a4bmr42674815ad.33.1778872855638; Fri, 15 May 2026 12:20:55 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 15 May 2026 12:19:24 -0700 In-Reply-To: <20260515191942.1892718-1-seanjc@google.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260515191942.1892718-1-seanjc@google.com> X-Mailer: git-send-email 2.54.0.563.g4f69b47b94-goog Message-ID: <20260515191942.1892718-24-seanjc@google.com> Subject: [PATCH v3 23/41] x86/kvmclock: Refactor handling of PVCLOCK_TSC_STABLE_BIT during kvmclock_init() From: Sean Christopherson To: Kiryl Shutsemau , Paolo Bonzini , Sean Christopherson , "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: Rick Edgecombe , Vitaly Kuznetsov , Broadcom internal kernel review list , Boris Ostrovsky , Stephen Boyd , 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 , Thomas Gleixner , David Woodhouse 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 8df6adcd6cd8..ccb2aff89b2f 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -306,7 +306,7 @@ static __init void kvm_sched_clock_init(bool stable) void __init kvmclock_init(void) { - u8 flags; + bool stable = false; if (!kvm_para_available() || !kvmclock) return; @@ -333,11 +333,18 @@ 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); -- 2.54.0.563.g4f69b47b94-goog