Re: [PATCH] x86/tdx: Override the tsc calibration for TDX VMs

[Huang, Kai]

>  
> +/**
> + * Determine TSC frequency via CPUID, else return 0.
> + */

Nit: looks you don't need the k-doc style comment here?

> +static unsigned long tdx_calibrate_tsc(void)
> +{
> +	unsigned int eax_denominator = 0, ebx_numerator = 0, ecx_hz = 0, edx = 0;
> +	unsigned int crystal_khz;
> +
> +	/* CPUID 15H TSC/Crystal ratio, plus optionally Crystal Hz */
> +	cpuid(0x15, &eax_denominator, &ebx_numerator, &ecx_hz, &edx);
> +
> +	if (ebx_numerator == 0 || eax_denominator == 0)
> +		return 0;
> +
> +	crystal_khz = ecx_hz / 1000;
> +
> +	/*
> +	 * TSC frequency reported directly by CPUID is a "hardware reported"
> +	 * frequency and is the most accurate one so far we have. This
> +	 * is considered a known frequency.
> +	 */
> +	if (crystal_khz != 0)
> +		setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
> +
> +	return crystal_khz * ebx_numerator / eax_denominator;
> +}
> +