Re: [PATCH v3 06/41] x86/acrn: Mark TSC frequency as known when using ACRN for calibration

[David Woodhouse <dwmw2@xxxxxxxxxxxxx>]

On Fri, 2026-05-15 at 12:19 -0700, Sean Christopherson wrote:
> Mark the TSC frequency as known when using ACRN's PV CPUID information.
> Per commit 81a71f51b89e ("x86/acrn: Set up timekeeping") and common sense,
> the TSC freq is explicitly provided by the hypervisor.
> 
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
>  arch/x86/kernel/cpu/acrn.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/kernel/cpu/acrn.c b/arch/x86/kernel/cpu/acrn.c
> index c1506cb87d8c..2da3de4d470e 100644
> --- a/arch/x86/kernel/cpu/acrn.c
> +++ b/arch/x86/kernel/cpu/acrn.c
> @@ -29,6 +29,7 @@ static void __init acrn_init_platform(void)
>       /* Install system interrupt handler for ACRN hypervisor callback */
>       sysvec_install(HYPERVISOR_CALLBACK_VECTOR, sysvec_acrn_hv_callback);
>  
> +     setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
>       tsc_register_calibration_routines(acrn_get_tsc_khz,
>                                         acrn_get_tsc_khz);

I'd feel slightly happier doing that from within acrn_get_tsc_khz()
itself.... which I note is 'static inline'. I'm vaguely surprised that
even builds (although it does). Probably nicer to move it explicitly
out of line in acrn.c though.

Most of that should be a comment on patch  2 of the series, I guess?

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