146 	 * it depends on the slow VM Reference Counter MSR (the Hyper-V TSC  in hv_stimer_init()
147 	 * page is not enbled in such a VM because the VM uses Invariant TSC  in hv_stimer_init()
149 	 * TSC page shared in very early boot).  in hv_stimer_init()
400  * the other that uses the TSC reference page feature as defined in the
402  * Hyper-V and 32-bit x86.  The TSC reference page version is preferred.
431 	 * subsection Refererence Counter, guarantees that the TSC and MSR  in read_hv_clock_tsc()
433 	 * to the MSR in case the TSC page indicates unavailability.  in read_hv_clock_tsc()
456 	/* Disable the TSC page */  in suspend_hv_clock_tsc()
467 	/* Re-enable the TSC page */  in resume_hv_clock_tsc()
477  * used to calculate time for hv tsc page based sched_clock, to account for
551 	 * If Hyper-V offers TSC_INVARIANT, then the virtualized TSC correctly  in hv_init_tsc_clocksource()
554 	 * Hyper-V Reference TSC rating, causing the generic TSC to be used.  in hv_init_tsc_clocksource()
556 	 * TSC will be preferred over the virtualized ARM64 arch counter.  in hv_init_tsc_clocksource()
569 	 * TSC page mapping works differently in root compared to guest.  in hv_init_tsc_clocksource()
578 	 * It worth mentioning, that TSC clocksource read function  in hv_init_tsc_clocksource()
580 	 * TSC page is zeroed (which is the case until the PFN is remapped) and  in hv_init_tsc_clocksource()
581 	 * thus TSC clocksource will work even without the real TSC page  in hv_init_tsc_clocksource()
596 	 * If TSC is invariant, then let it stay as the sched clock since it  in hv_init_tsc_clocksource()
597 	 * will be faster than reading the TSC page. But if not invariant, use  in hv_init_tsc_clocksource()
598 	 * the TSC page so that live migrations across hosts with different  in hv_init_tsc_clocksource()
610 	 * Try to set up the TSC page clocksource, then the MSR clocksource.  in hv_init_clocksource()
631 		WARN(1, "%s: attempt to remap TSC page in guest partition\n",  in hv_remap_tsc_clocksource()
639 		pr_err("Failed to remap Hyper-V TSC page.\n");  in hv_remap_tsc_clocksource()