Messages in this thread | | | From | Vitaly Kuznetsov <> | Subject | Re: [PATCH] x86/vmware: avoid TSC recalibration | Date | Tue, 05 Jan 2021 14:06:08 +0100 |
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Alexey Makhalov <amakhalov@vmware.com> writes:
> When TSC frequency is known (retrieved from hypervisor), we should skip > TSC refined calibration by setting X86_FEATURE_TSC_KNOWN_FREQ. > > Signed-off-by: Alexey Makhalov <amakhalov@vmware.com> > --- > arch/x86/kernel/cpu/vmware.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c > index c6ede3b3d302..83164110ccc5 100644 > --- a/arch/x86/kernel/cpu/vmware.c > +++ b/arch/x86/kernel/cpu/vmware.c > @@ -378,6 +378,8 @@ static void __init vmware_set_capabilities(void) > { > setup_force_cpu_cap(X86_FEATURE_CONSTANT_TSC); > setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE); > + if (vmware_tsc_khz) > + setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); > if (vmware_hypercall_mode == CPUID_VMWARE_FEATURES_ECX_VMCALL) > setup_force_cpu_cap(X86_FEATURE_VMCALL); > else if (vmware_hypercall_mode == CPUID_VMWARE_FEATURES_ECX_VMMCALL)
The same trick is being used in Xen/Jailhouse/KVM code already and Hyper-V overwrites x86_platform.calibrate_tsc/x86_platform.calibrate_cpu hooks to basically achive the same goal. Should we maybe introduce a flag in 'struct hypervisor_x86' or something like that to unify all this?
Just a suggestion.
-- Vitaly
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