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
26 #include <asm/hyperv-tlfs.h>
33  * If false, we're using the old mechanism for stimer0 interrupts
35  * mechanism is used when running on older versions of Hyper-V
36  * that don't support Direct Mode. While Hyper-V provides
43  * However, for legacy versions of Hyper-V when Direct Mode
50 static int stimer0_irq = -1;
63 	ce->event_handler(ce);  in hv_stimer0_isr()
69  * per-cpu interrupts, which also implies Direct Mode.
127  * hv_stimer_init - Per-cpu initialization of the clockevent
137 	ce->name = "Hyper-V clockevent";  in hv_stimer_init()
138 	ce->features = CLOCK_EVT_FEAT_ONESHOT;  in hv_stimer_init()
139 	ce->cpumask = cpumask_of(cpu);  in hv_stimer_init()
142 	 * Lower the rating of the Hyper-V timer in a TDX VM without paravisor,  in hv_stimer_init()
144 	 * such a VM. The Hyper-V timer is not preferred in such a VM because  in hv_stimer_init()
145 	 * it depends on the slow VM Reference Counter MSR (the Hyper-V TSC  in hv_stimer_init()
147 	 * as a better clocksource and it's challenging to mark the Hyper-V  in hv_stimer_init()
151 		ce->rating = 90;  in hv_stimer_init()
153 		ce->rating = 1000;  in hv_stimer_init()
155 	ce->set_state_shutdown = hv_ce_shutdown;  in hv_stimer_init()
156 	ce->set_state_oneshot = hv_ce_set_oneshot;  in hv_stimer_init()
157 	ce->set_next_event = hv_ce_set_next_event;  in hv_stimer_init()
167  * hv_stimer_cleanup - Per-cpu cleanup of the clockevent
180 	 * must unbind the stimer-based clockevent device so  in hv_stimer_cleanup()
203  * they don't support per-cpu IRQs (such as x86/x64).
214 /* Called only on architectures with per-cpu IRQs (i.e., not x86/x64) */
222 		pr_err("Can't register Hyper-V stimer0 GSI. Error %d", ret);  in hv_setup_stimer0_irq()
228 		"Hyper-V stimer0", &stimer0_evt);  in hv_setup_stimer0_irq()
230 		pr_err("Can't request Hyper-V stimer0 IRQ %d. Error %d",  in hv_setup_stimer0_irq()
233 		stimer0_irq = -1;  in hv_setup_stimer0_irq()
240 	if (stimer0_irq == -1) {  in hv_remove_stimer0_irq()
245 		stimer0_irq = -1;  in hv_remove_stimer0_irq()
259 /* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
266 	 * Hyper-V on x86.  In that case, return as error as Linux will use a  in hv_stimer_alloc()
270 		return -EINVAL;  in hv_stimer_alloc()
274 		return -ENOMEM;  in hv_stimer_alloc()
280 	 * If Direct Mode isn't enabled, the remainder of the initialization  in hv_stimer_alloc()
295 	 * Since we are in Direct Mode, stimer initialization  in hv_stimer_alloc()
316  * hv_stimer_legacy_init -- Called from the VMbus driver to handle
339  * hv_stimer_legacy_cleanup -- Called from the VMbus driver to
374 		stimer0_irq = -1;  in hv_stimer_global_cleanup()
397  * Code and definitions for the Hyper-V clocksources.  Two
398  * clocksources are defined: one that reads the Hyper-V defined MSR, and
401  * Hyper-V and 32-bit x86.  The TSC reference page version is preferred.
429 	 * The Hyper-V Top-Level Function Spec (TLFS), section Timers,  in read_hv_clock_tsc()
447 	return (read_hv_clock_tsc() - hv_sched_clock_offset) *  in read_hv_sched_clock_tsc()
466 	/* Re-enable the TSC page */  in resume_hv_clock_tsc()
518 	 * We're on an architecture with generic sched clock (not x86/x64).  in hv_setup_sched_clock()
519 	 * The Hyper-V sched clock read function returns nanoseconds, not  in hv_setup_sched_clock()
520 	 * the normal 100ns units of the Hyper-V synthetic clock.  in hv_setup_sched_clock()
527 	/* We're on x86/x64 *and* using PV ops */  in hv_setup_sched_clock()
539 	 * If Hyper-V offers TSC_INVARIANT, then the virtualized TSC correctly  in hv_init_tsc_clocksource()
542 	 * Hyper-V Reference TSC rating, causing the generic TSC to be used.  in hv_init_tsc_clocksource()
543 	 * TSC_INVARIANT is not offered on ARM64, so the Hyper-V Reference  in hv_init_tsc_clocksource()
558 	 * - In guest partition the guest PFN has to be passed to the  in hv_init_tsc_clocksource()
560 	 * - In root partition it's other way around: it has to map the PFN  in hv_init_tsc_clocksource()
567 	 * (read_hv_clock_tsc) has a MSR-based fallback mechanism, used when  in hv_init_tsc_clocksource()
600 	 * versions of Hyper-V on x86.  In that case we won't have a Hyper-V  in hv_init_clocksource()
627 		pr_err("Failed to remap Hyper-V TSC page.\n");  in hv_remap_tsc_clocksource()