RE: [PATCH 1/1] x86/hyperv: Set X86_FEATURE_TSC_KNOWN_FREQ when Hyper-V provides frequency

[Michael Kelley]

From: Wei Liu <wei.liu@xxxxxxxxxx> Sent: Friday, August 2, 2024 4:50 PM
> 
> On Tue, Jun 11, 2024 at 07:51:48AM -0700, Roman Kisel wrote:
> >
> >
> > On 6/5/2024 7:55 PM, mhkelley58@xxxxxxxxx wrote:
> > > From: Michael Kelley <mhklinux@xxxxxxxxxxx>
> > >
> > > 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>
> > > ---
> > >   arch/x86/kernel/cpu/mshyperv.c | 1 +
> > >   1 file changed, 1 insertion(+)
> > >
> > > diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> > > index e0fd57a8ba84..c3e38eaf6d2f 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) {
> >
> > LGTM
> >
> > Reviewed-by: Roman Kisel <romank@xxxxxxxxxxxxxxxxxxx>
> 
> Applied to hyperv-fixes. Thanks!

Wei --

hyperv-fixes isn't showing this patch, or any of the others that your
emails said you applied last Friday.  Hence the patches aren't in
linux-next either.  Did something go awry?

Michael