Commit 64cde6fe authored Dec 23, 2024 by Michael Kelley Committed by Qi Xi Dec 23, 2024

x86/hyperv: Set X86_FEATURE_TSC_KNOWN_FREQ when Hyper-V provides frequency

stable inclusion
from stable-v4.19.323
commit 1da08d443212eba1f731b3f163c5b23ec1c882c1
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IBBN6V

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1da08d443212eba1f731b3f163c5b23ec1c882c1



--------------------------------

[ Upstream commit 8fcc514809de41153b43ccbe1a0cdf7f72b78e7e ]

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 <mhklinux@outlook.com>
Reviewed-by: Roman Kisel <romank@linux.microsoft.com>
Link: https://lore.kernel.org/r/20240606025559.1631-1-mhklinux@outlook.com


Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20240606025559.1631-1-mhklinux@outlook.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Qi Xi <xiqi2@huawei.com>

parent 765b1322

arch/x86/kernel/cpu/mshyperv.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -243,6 +243,7 @@ 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.hints & HV_X64_ENLIGHTENED_VMCS_RECOMMENDED) {