Re: [PATCH linux-next] x86/xen/time: prefer tsc as clocksource when it is invariant

[Boris Ostrovsky]

On 12/8/22 11:36 AM, Krister Johansen wrote:
> +	/*
> +	 * As Dom0 is never moved, no penalty on using TSC there.
> +	 *
> +	 * If the guest has invariant tsc, then set xen_clocksource rating
> +	 * below that of the tsc so that the system prefers tsc instead.  This
> +	 * check excludes PV domains, because PV is unable to guarantee that the
> +	 * guest's cpuid call has been intercepted by the hypervisor.
> +	 */
> +	if (xen_initial_domain()) {
>   		xen_clocksource.rating = 275;
> +	} else if ((xen_hvm_domain() || xen_pvh_domain()) &&
> +	    boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
> +	    boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
> +	    !check_tsc_unstable()) {
> +		xen_clocksource.rating = 299;
> +	}


What if RDTSC is intercepted?


-boris