From patchwork Thu Feb 27 02:18:39 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 13993610 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C8944C19F32 for ; Thu, 27 Feb 2025 02:26:01 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.897484.1306228 (Exim 4.92) (envelope-from ) id 1tnTb0-0007vm-QS; Thu, 27 Feb 2025 02:25:54 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 897484.1306228; Thu, 27 Feb 2025 02:25:54 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1tnTb0-0007qm-3u; Thu, 27 Feb 2025 02:25:54 +0000 Received: by outflank-mailman (input) for mailman id 897484; Thu, 27 Feb 2025 02:25:51 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1tnTV7-0005qU-Fn for xen-devel@lists.xenproject.org; Thu, 27 Feb 2025 02:19:49 +0000 Received: from mail-pj1-x1049.google.com (mail-pj1-x1049.google.com [2607:f8b0:4864:20::1049]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 4ec514aa-f4b1-11ef-9aaf-95dc52dad729; Thu, 27 Feb 2025 03:19:44 +0100 (CET) Received: by mail-pj1-x1049.google.com with SMTP id 98e67ed59e1d1-2f81a0d0a18so1091531a91.3 for ; Wed, 26 Feb 2025 18:19:44 -0800 (PST) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 4ec514aa-f4b1-11ef-9aaf-95dc52dad729 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1740622783; x=1741227583; darn=lists.xenproject.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=Za0nk5QeJovZveNmDgTJSzh3R0hb/7p0/gaKYZ4C/Vs=; b=Q5q2J/VjzoU+MMZ2merUpsvt4BFtgiTRf0sDvkFD4U6xwqPnu1LSys7fgsAf5yR9yF SpoJ53WspMLmuOZtGPm3xrFxJJZ8kieBtnrVM6qYjcYhx0FdozfXu9j9rKxfy2BwnnAi f/jDtWh5RFXyKfUqxuNjXdmDQUNupJhGvbWePrzSWnmc9ZaFfGqrSFI6m66dp8a8I+Ya HcxceJ8PLFygCaMItvADDlFnPSclPKU74xYspK/yAeYDS49bHXl/YJs7ehzCzKDXoclt zM5vmeejTDfPKadKC5Cd8CmEEig7avwdjc6zymHn59xz4iZcwr0LHms8+EPjpRsTQ9Jl jYXg== 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=nHk3UCOJjswsWO03CILbmS4cfSzyTo9RuIO33fM94MdzwR0tdLZE5y8YOvbFI0hiWo JATZoNPys0SX7MpR313VRZcuvZ8jfgnV5Ka0MwZOqP1/v0hpcXgQezRFaYP1fud1jKST 48HbNb8UKENAbzAjMxTPy5kxBYuAKEMs78FgVtcIgcYfzdKtrceIqPkXVQBoJVh2SdfI cHu/XXlhSOcRRBr8FdlN4xclEpki49mALkPbviiVjRpWbxgszhpqMF7BpYUuxFCKlbTy in8j/Zgi4buiEaU98npoV1auDEAq3fg0NfTfJJOoHF6zpkdFWqUaz9uAMULnOX0LwPb2 IC3A== X-Forwarded-Encrypted: i=1; AJvYcCWMHLYiQxxbkhqGy7LK7udu/zWNHrjCOtVPTxcF3zoFl7PHC1VX2K4q+Cl2xxboeSCE+7jkjmhvhYg=@lists.xenproject.org X-Gm-Message-State: AOJu0Yy5wS1vQsgsMn3bShGAyoz1pi6l3UtGIn+0UPLL9Y+WDnFrGen5 JGDevl6vL+nTPJQI/zDvmLmotnidur3aGxbeDH/u9lZz23IntuTN0+uoDLYeLlE4z9g1io/5q+E QqQ== 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> 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 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);