From: Michael Kelley Date: Mon, 9 May 2022 15:44:23 +0000 (-0700) Subject: x86/hyperv: Disable hardlockup detector by default in Hyper-V guests X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=f1f8288d19d03af9d03db219c23d07a6e8ecd51b;p=linux.git x86/hyperv: Disable hardlockup detector by default in Hyper-V guests In newer versions of Hyper-V, the x86/x64 PMU can be virtualized into guest VMs by explicitly enabling it. Linux kernels are typically built to automatically enable the hardlockup detector if the PMU is found. To prevent the possibility of false positives due to the vagaries of VM scheduling, disable the PMU-based hardlockup detector by default in a VM on Hyper-V. The hardlockup detector can still be enabled by overriding the default with the nmi_watchdog=1 option on the kernel boot line or via sysctl at runtime. This change mimics the approach taken with KVM guests in commit 692297d8f968 ("watchdog: introduce the hardlockup_detector_disable() function"). Linux on ARM64 does not provide a PMU-based hardlockup detector, so there's no corresponding disable in the Hyper-V init code on ARM64. Signed-off-by: Michael Kelley Link: https://lore.kernel.org/r/1652111063-6535-1-git-send-email-mikelley@microsoft.com Signed-off-by: Wei Liu --- diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index 4b67094215bba..16dad62c8155b 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -465,6 +465,8 @@ static void __init ms_hyperv_init_platform(void) */ if (!(ms_hyperv.features & HV_ACCESS_TSC_INVARIANT)) mark_tsc_unstable("running on Hyper-V"); + + hardlockup_detector_disable(); } static bool __init ms_hyperv_x2apic_available(void)