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client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by CH1PEPF0000A34C.mail.protection.outlook.com (10.167.244.6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8230.7 via Frontend Transport; Tue, 3 Dec 2024 09:01:49 +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; Tue, 3 Dec 2024 03:01:45 -0600 From: Nikunj A Dadhania To: , , , , CC: , , , , , , , Alexey Makhalov , "Juergen Gross" , Boris Ostrovsky Subject: [PATCH v15 11/13] tsc: Switch to native sched clock Date: Tue, 3 Dec 2024 14:30:43 +0530 Message-ID: <20241203090045.942078-12-nikunj@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20241203090045.942078-1-nikunj@amd.com> References: <20241203090045.942078-1-nikunj@amd.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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: CH1PEPF0000A34C:EE_|DM4PR12MB6088:EE_ X-MS-Office365-Filtering-Correlation-Id: b61b4ab8-f2cc-4940-4de4-08dd13791f54 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|1800799024|82310400026|7416014|376014; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(36860700013)(1800799024)(82310400026)(7416014)(376014);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Dec 2024 09:01:49.3442 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: b61b4ab8-f2cc-4940-4de4-08dd13791f54 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: CH1PEPF0000A34C.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB6088 Although the kernel switches over to stable TSC clocksource instead of PV clocksource, the scheduler still keeps on using PV clocks as the sched clock source. This is because KVM, Xen and VMWare, switch the paravirt sched clock handler in their init routines. HyperV is the only PV clock source that checks if the platform provides an invariant TSC and does not switch to PV sched clock. When switching back to stable TSC, restore the scheduler clock to native_sched_clock(). As the clock selection happens in the stop machine context, schedule delayed work to update the static_call() Cc: Alexey Makhalov Cc: Juergen Gross Cc: Boris Ostrovsky Signed-off-by: Nikunj A Dadhania --- arch/x86/kernel/tsc.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 900edcde0c9e..a337c7e0b26e 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -273,10 +273,25 @@ bool using_native_sched_clock(void) { return static_call_query(pv_sched_clock) == native_sched_clock; } + +static void enable_native_sc_work(struct work_struct *work) +{ + pr_info("using native sched clock\n"); + paravirt_set_sched_clock(native_sched_clock); +} +static DECLARE_DELAYED_WORK(enable_native_sc, enable_native_sc_work); + +static void enable_native_sched_clock(void) +{ + if (!using_native_sched_clock()) + schedule_delayed_work(&enable_native_sc, 0); +} #else u64 sched_clock_noinstr(void) __attribute__((alias("native_sched_clock"))); bool using_native_sched_clock(void) { return true; } + +static void enable_native_sched_clock(void) { } #endif notrace u64 sched_clock(void) @@ -1158,6 +1173,10 @@ static void tsc_cs_tick_stable(struct clocksource *cs) static int tsc_cs_enable(struct clocksource *cs) { vclocks_set_used(VDSO_CLOCKMODE_TSC); + + /* Restore native_sched_clock() when switching to TSC */ + enable_native_sched_clock(); + return 0; }