1 // SPDX-License-Identifier: GPL-2.0
5  * provided by the Hyper-V hypervisor to guest VMs, as described
6  * in the Hyper-V Top Level Functional Spec (TLFS). This driver
37  * mechanism is used when running on older versions of Hyper-V
38  * that don't support Direct Mode. While Hyper-V provides
45  * However, for legacy versions of Hyper-V when Direct Mode
52 static int stimer0_irq = -1;
65 	ce->event_handler(ce);  in hv_stimer0_isr()
71  * per-cpu interrupts, which also implies Direct Mode.
129  * hv_stimer_init - Per-cpu initialization of the clockevent
139 	ce->name = "Hyper-V clockevent";  in hv_stimer_init()
140 	ce->features = CLOCK_EVT_FEAT_ONESHOT;  in hv_stimer_init()
141 	ce->cpumask = cpumask_of(cpu);  in hv_stimer_init()
144 	 * Lower the rating of the Hyper-V timer in a TDX VM without paravisor,  in hv_stimer_init()
146 	 * such a VM. The Hyper-V timer is not preferred in such a VM because  in hv_stimer_init()
147 	 * it depends on the slow VM Reference Counter MSR (the Hyper-V TSC  in hv_stimer_init()
148 	 * page is not enbled in such a VM because the VM uses Invariant TSC  in hv_stimer_init()
149 	 * as a better clocksource and it's challenging to mark the Hyper-V  in hv_stimer_init()
150 	 * TSC page shared in very early boot).  in hv_stimer_init()
153 		ce->rating = 90;  in hv_stimer_init()
155 		ce->rating = 1000;  in hv_stimer_init()
157 	ce->set_state_shutdown = hv_ce_shutdown;  in hv_stimer_init()
158 	ce->set_state_oneshot = hv_ce_set_oneshot;  in hv_stimer_init()
159 	ce->set_next_event = hv_ce_set_next_event;  in hv_stimer_init()
169  * hv_stimer_cleanup - Per-cpu cleanup of the clockevent
182 	 * must unbind the stimer-based clockevent device so  in hv_stimer_cleanup()
205  * they don't support per-cpu IRQs (such as x86/x64).
216 /* Called only on architectures with per-cpu IRQs (i.e., not x86/x64) */
224 		pr_err("Can't register Hyper-V stimer0 GSI. Error %d", ret);  in hv_setup_stimer0_irq()
230 		"Hyper-V stimer0", &stimer0_evt);  in hv_setup_stimer0_irq()
232 		pr_err("Can't request Hyper-V stimer0 IRQ %d. Error %d",  in hv_setup_stimer0_irq()
235 		stimer0_irq = -1;  in hv_setup_stimer0_irq()
242 	if (stimer0_irq == -1) {  in hv_remove_stimer0_irq()
247 		stimer0_irq = -1;  in hv_remove_stimer0_irq()
261 /* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
268 	 * Hyper-V on x86.  In that case, return as error as Linux will use a  in hv_stimer_alloc()
269 	 * clockevent based on emulated LAPIC timer hardware.  in hv_stimer_alloc()
272 		return -EINVAL;  in hv_stimer_alloc()
276 		return -ENOMEM;  in hv_stimer_alloc()
318  * hv_stimer_legacy_init -- Called from the VMbus driver to handle
341  * hv_stimer_legacy_cleanup -- Called from the VMbus driver to
376 		stimer0_irq = -1;  in hv_stimer_global_cleanup()
399  * Code and definitions for the Hyper-V clocksources.  Two
400  * clocksources are defined: one that reads the Hyper-V defined MSR, and
401  * the other that uses the TSC reference page feature as defined in the
403  * Hyper-V and 32-bit x86.  The TSC reference page version is preferred.
407 	struct ms_hyperv_tsc_page page;  member
411 static struct ms_hyperv_tsc_page *tsc_page = &tsc_pg.page;
431 	 * The Hyper-V Top-Level Function Spec (TLFS), section Timers,  in read_hv_clock_tsc()
434 	 * to the MSR in case the TSC page indicates unavailability.  in read_hv_clock_tsc()
449 	return (read_hv_clock_tsc() - hv_sched_clock_offset) *  in read_hv_sched_clock_tsc()
457 	/* Disable the TSC page */  in suspend_hv_clock_tsc()
468 	/* Re-enable the TSC page */  in resume_hv_clock_tsc()
478  * used to calculate time for hv tsc page based sched_clock, to account for
483 	hv_sched_clock_offset -= offset;  in hv_adj_sched_clock_offset()
532 	 * The Hyper-V sched clock read function returns nanoseconds, not  in hv_setup_sched_clock()
533 	 * the normal 100ns units of the Hyper-V synthetic clock.  in hv_setup_sched_clock()
552 	 * If Hyper-V offers TSC_INVARIANT, then the virtualized TSC correctly  in hv_init_tsc_clocksource()
555 	 * Hyper-V Reference TSC rating, causing the generic TSC to be used.  in hv_init_tsc_clocksource()
556 	 * TSC_INVARIANT is not offered on ARM64, so the Hyper-V Reference  in hv_init_tsc_clocksource()
570 	 * TSC page mapping works differently in root compared to guest.  in hv_init_tsc_clocksource()
571 	 * - In guest partition the guest PFN has to be passed to the  in hv_init_tsc_clocksource()
573 	 * - In root partition it's other way around: it has to map the PFN  in hv_init_tsc_clocksource()
577 	 *   page later in hv_remap_tsc_clocksource().  in hv_init_tsc_clocksource()
580 	 * (read_hv_clock_tsc) has a MSR-based fallback mechanism, used when  in hv_init_tsc_clocksource()
581 	 * TSC page is zeroed (which is the case until the PFN is remapped) and  in hv_init_tsc_clocksource()
582 	 * thus TSC clocksource will work even without the real TSC page  in hv_init_tsc_clocksource()
598 	 * will be faster than reading the TSC page. But if not invariant, use  in hv_init_tsc_clocksource()
599 	 * the TSC page so that live migrations across hosts with different  in hv_init_tsc_clocksource()
611 	 * Try to set up the TSC page clocksource, then the MSR clocksource.  in hv_init_clocksource()
613 	 * versions of Hyper-V on x86.  In that case we won't have a Hyper-V  in hv_init_clocksource()
614 	 * clocksource, but Linux will still run with a clocksource based  in hv_init_clocksource()
632 		WARN(1, "%s: attempt to remap TSC page in guest partition\n",  in hv_remap_tsc_clocksource()
640 		pr_err("Failed to remap Hyper-V TSC page.\n");  in hv_remap_tsc_clocksource()