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Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by SJ1PEPF00001CE9.mail.protection.outlook.com (10.167.242.25) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8093.14 via Frontend Transport; Mon, 28 Oct 2024 05:35:48 +0000 Received: from gomati.amd.com (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.39; Mon, 28 Oct 2024 00:35:41 -0500 From: Nikunj A Dadhania To: , , , , CC: , , , , , , , Alexey Makhalov , "Juergen Gross" , Boris Ostrovsky Subject: [PATCH v14 10/13] tsc: Upgrade TSC clocksource rating Date: Mon, 28 Oct 2024 11:04:28 +0530 Message-ID: <20241028053431.3439593-11-nikunj@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20241028053431.3439593-1-nikunj@amd.com> References: <20241028053431.3439593-1-nikunj@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: SATLEXMB03.amd.com (10.181.40.144) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ1PEPF00001CE9:EE_|CY5PR12MB6177:EE_ X-MS-Office365-Filtering-Correlation-Id: 2d9cc462-70cd-4e65-73d3-08dcf71260e7 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|7416014|36860700013|82310400026; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 Oct 2024 05:35:48.5302 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2d9cc462-70cd-4e65-73d3-08dcf71260e7 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SJ1PEPF00001CE9.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY5PR12MB6177 Content-Type: text/plain; charset="utf-8" In virtualized environments running on modern CPUs, the underlying platforms guarantees to have a stable, always running TSC, i.e. that the TSC is a superior timesource as compared to other clock sources (such as kvmclock, HPET, ACPI timer, APIC, etc.). Upgrade the rating of the early and regular clock source to prefer TSC over other clock sources when TSC is invariant, non-stop and stable. Cc: Alexey Makhalov Cc: Juergen Gross Cc: Boris Ostrovsky Suggested-by: Thomas Gleixner Signed-off-by: Nikunj A Dadhania --- arch/x86/kernel/tsc.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 730cbbd4554e..cf29ede4ee80 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -1264,6 +1264,21 @@ static void __init check_system_tsc_reliable(void) tsc_disable_clocksource_watchdog(); } =20 +static void __init upgrade_clock_rating(struct clocksource *tsc_early, + struct clocksource *tsc) +{ + /* + * Upgrade the clock rating for TSC early and regular clocksource when + * the underlying platform provides non-stop, invaraint and stable TSC. + */ + if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && + boot_cpu_has(X86_FEATURE_NONSTOP_TSC) && + !tsc_unstable) { + tsc_early->rating =3D 449; + tsc->rating =3D 450; + } +} + /* * Make an educated guess if the TSC is trustworthy and synchronized * over all CPUs. @@ -1565,6 +1580,8 @@ void __init tsc_init(void) if (tsc_clocksource_reliable || no_tsc_watchdog) tsc_disable_clocksource_watchdog(); =20 + upgrade_clock_rating(&clocksource_tsc_early, &clocksource_tsc); + clocksource_register_khz(&clocksource_tsc_early, tsc_khz); detect_art(); } --=20 2.34.1