This is a note to let you know that I've just added the patch titled
x86/hyperv: Set X86_FEATURE_TSC_KNOWN_FREQ when Hyper-V provides frequency
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-hyperv-set-x86_feature_tsc_known_freq-when-hyper.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 9a2470548bfca6528d3fbee4cf29967c20fc120b
Author: Michael Kelley <mhklinux@xxxxxxxxxxx>
Date: Wed Jun 5 19:55:59 2024 -0700
x86/hyperv: Set X86_FEATURE_TSC_KNOWN_FREQ when Hyper-V provides frequency
[ 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@xxxxxxxxxxx>
Reviewed-by: Roman Kisel <romank@xxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240606025559.1631-1-mhklinux@xxxxxxxxxxx
Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx>
Message-ID: <20240606025559.1631-1-mhklinux@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index f8b0fa2dbe374..b43f25b3c99d3 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -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) {
