From: Michael Kelley Date: Thu, 6 Jun 2024 02:55:59 +0000 (-0700) Subject: x86/hyperv: Set X86_FEATURE_TSC_KNOWN_FREQ when Hyper-V provides frequency X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=8fcc514809de41153b43ccbe1a0cdf7f72b78e7e;p=users%2Fjedix%2Flinux-maple.git x86/hyperv: Set X86_FEATURE_TSC_KNOWN_FREQ when Hyper-V provides frequency A Linux guest on Hyper-V gets the TSC frequency from a synthetic MSR, if available. In this case, set X86_FEATURE_TSC_KNOWN_FREQ so that Linux doesn't unnecessarily do refined TSC calibration when setting up the TSC clocksource. With this change, a message such as this is no longer output during boot when the TSC is used as the clocksource: [ 1.115141] tsc: Refined TSC clocksource calibration: 2918.408 MHz Furthermore, the guest and host will have exactly the same view of the TSC frequency, which is important for features such as the TSC deadline timer that are emulated by the Hyper-V host. Signed-off-by: Michael Kelley Reviewed-by: Roman Kisel Link: https://lore.kernel.org/r/20240606025559.1631-1-mhklinux@outlook.com Signed-off-by: Wei Liu Message-ID: <20240606025559.1631-1-mhklinux@outlook.com> --- diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index 954b7cbfa2f02..6a9aa057f9ca0 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -424,6 +424,7 @@ static void __init ms_hyperv_init_platform(void) ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) { x86_platform.calibrate_tsc = hv_get_tsc_khz; x86_platform.calibrate_cpu = hv_get_tsc_khz; + setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); } if (ms_hyperv.priv_high & HV_ISOLATION) {