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Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)), "H. Peter Anvin" , Daniel Lezcano , linux-hyperv@vger.kernel.org (open list:Hyper-V/Azure CORE AND DRIVERS), linux-kernel@vger.kernel.org (open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)) Cc: stable@vger.kernel.org Subject: [PATCH] clocksource: hyper-v: Use lapic timer in a TDX VM without paravisor Date: Tue, 18 Jun 2024 17:25:04 -0700 Message-Id: <20240619002504.3652-1-decui@microsoft.com> X-Mailer: git-send-email 2.25.1 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: MW4PR04CA0195.namprd04.prod.outlook.com (2603:10b6:303:86::20) To PH8PR21MB3902.namprd21.prod.outlook.com (2603:10b6:510:250::11) Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH8PR21MB3902:EE_|LV3PR21MB4254:EE_ X-MS-Office365-Filtering-Correlation-Id: 4dd5bd55-a03a-45c0-66fe-08dc8ff6625e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230037|52116011|376011|1800799021|366013|7416011|921017; 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Lower the rating of the Hyper-V timer so the local APIC timer becomes the the default timer in such a VM. This change should cause no perceivable performance difference. Cc: stable@vger.kernel.org # 6.6+ Signed-off-by: Dexuan Cui --- arch/x86/kernel/cpu/mshyperv.c | 6 +++++- drivers/clocksource/hyperv_timer.c | 16 +++++++++++++++- 2 files changed, 20 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index e0fd57a8ba840..745af47ca0459 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -449,9 +449,13 @@ static void __init ms_hyperv_init_platform(void) ms_hyperv.hints &= ~HV_X64_APIC_ACCESS_RECOMMENDED; if (!ms_hyperv.paravisor_present) { - /* To be supported: more work is required. */ + /* Use Invariant TSC as a better clocksource. */ ms_hyperv.features &= ~HV_MSR_REFERENCE_TSC_AVAILABLE; + /* Use the Ref Counter in case Invariant TSC is unavailable. */ + if (!(ms_hyperv.features & HV_ACCESS_TSC_INVARIANT)) + pr_warn("Hyper-V: Invariant TSC is unavailable\n"); + /* HV_MSR_CRASH_CTL is unsupported. */ ms_hyperv.misc_features &= ~HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE; diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c index b2a080647e413..99177835cadec 100644 --- a/drivers/clocksource/hyperv_timer.c +++ b/drivers/clocksource/hyperv_timer.c @@ -137,7 +137,21 @@ static int hv_stimer_init(unsigned int cpu) ce->name = "Hyper-V clockevent"; ce->features = CLOCK_EVT_FEAT_ONESHOT; ce->cpumask = cpumask_of(cpu); - ce->rating = 1000; + + /* + * Lower the rating of the Hyper-V timer in a TDX VM without paravisor, + * so the local APIC timer (lapic_clockevent) is the default timer in + * such a VM. The Hyper-V timer is not preferred in such a VM because + * it depends on the slow VM Reference Counter MSR (the Hyper-V TSC + * page is not enbled in such a VM because the VM uses Invariant TSC + * as a better clocksource and it's challenging to mark the Hyper-V + * TSC page shared in very early boot). + */ + if (!ms_hyperv.paravisor_present && hv_isolation_type_tdx()) + ce->rating = 90; + else + ce->rating = 1000; + ce->set_state_shutdown = hv_ce_shutdown; ce->set_state_oneshot = hv_ce_set_oneshot; ce->set_next_event = hv_ce_set_next_event; -- 2.25.1