diff options
Diffstat (limited to 'drivers/clocksource/hyperv_timer.c')
| -rw-r--r-- | drivers/clocksource/hyperv_timer.c | 614 |
1 files changed, 614 insertions, 0 deletions
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c new file mode 100644 index 000000000..8ff7cd4e2 --- /dev/null +++ b/drivers/clocksource/hyperv_timer.c @@ -0,0 +1,614 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * Clocksource driver for the synthetic counter and timers + * provided by the Hyper-V hypervisor to guest VMs, as described + * in the Hyper-V Top Level Functional Spec (TLFS). This driver + * is instruction set architecture independent. + * + * Copyright (C) 2019, Microsoft, Inc. + * + * Author: Michael Kelley <mikelley@microsoft.com> + */ + +#include <linux/percpu.h> +#include <linux/cpumask.h> +#include <linux/clockchips.h> +#include <linux/clocksource.h> +#include <linux/sched_clock.h> +#include <linux/mm.h> +#include <linux/cpuhotplug.h> +#include <linux/interrupt.h> +#include <linux/irq.h> +#include <linux/acpi.h> +#include <linux/hyperv.h> +#include <clocksource/hyperv_timer.h> +#include <asm/hyperv-tlfs.h> +#include <asm/mshyperv.h> + +static struct clock_event_device __percpu *hv_clock_event; +static u64 hv_sched_clock_offset __ro_after_init; + +/* + * If false, we're using the old mechanism for stimer0 interrupts + * where it sends a VMbus message when it expires. The old + * mechanism is used when running on older versions of Hyper-V + * that don't support Direct Mode. While Hyper-V provides + * four stimer's per CPU, Linux uses only stimer0. + * + * Because Direct Mode does not require processing a VMbus + * message, stimer interrupts can be enabled earlier in the + * process of booting a CPU, and consistent with when timer + * interrupts are enabled for other clocksource drivers. + * However, for legacy versions of Hyper-V when Direct Mode + * is not enabled, setting up stimer interrupts must be + * delayed until VMbus is initialized and can process the + * interrupt message. + */ +static bool direct_mode_enabled; + +static int stimer0_irq = -1; +static int stimer0_message_sint; +static __maybe_unused DEFINE_PER_CPU(long, stimer0_evt); + +/* + * Common code for stimer0 interrupts coming via Direct Mode or + * as a VMbus message. + */ +void hv_stimer0_isr(void) +{ + struct clock_event_device *ce; + + ce = this_cpu_ptr(hv_clock_event); + ce->event_handler(ce); +} +EXPORT_SYMBOL_GPL(hv_stimer0_isr); + +/* + * stimer0 interrupt handler for architectures that support + * per-cpu interrupts, which also implies Direct Mode. + */ +static irqreturn_t __maybe_unused hv_stimer0_percpu_isr(int irq, void *dev_id) +{ + hv_stimer0_isr(); + return IRQ_HANDLED; +} + +static int hv_ce_set_next_event(unsigned long delta, + struct clock_event_device *evt) +{ + u64 current_tick; + + current_tick = hv_read_reference_counter(); + current_tick += delta; + hv_set_register(HV_REGISTER_STIMER0_COUNT, current_tick); + return 0; +} + +static int hv_ce_shutdown(struct clock_event_device *evt) +{ + hv_set_register(HV_REGISTER_STIMER0_COUNT, 0); + hv_set_register(HV_REGISTER_STIMER0_CONFIG, 0); + if (direct_mode_enabled && stimer0_irq >= 0) + disable_percpu_irq(stimer0_irq); + + return 0; +} + +static int hv_ce_set_oneshot(struct clock_event_device *evt) +{ + union hv_stimer_config timer_cfg; + + timer_cfg.as_uint64 = 0; + timer_cfg.enable = 1; + timer_cfg.auto_enable = 1; + if (direct_mode_enabled) { + /* + * When it expires, the timer will directly interrupt + * on the specified hardware vector/IRQ. + */ + timer_cfg.direct_mode = 1; + timer_cfg.apic_vector = HYPERV_STIMER0_VECTOR; + if (stimer0_irq >= 0) + enable_percpu_irq(stimer0_irq, IRQ_TYPE_NONE); + } else { + /* + * When it expires, the timer will generate a VMbus message, + * to be handled by the normal VMbus interrupt handler. + */ + timer_cfg.direct_mode = 0; + timer_cfg.sintx = stimer0_message_sint; + } + hv_set_register(HV_REGISTER_STIMER0_CONFIG, timer_cfg.as_uint64); + return 0; +} + +/* + * hv_stimer_init - Per-cpu initialization of the clockevent + */ +static int hv_stimer_init(unsigned int cpu) +{ + struct clock_event_device *ce; + + if (!hv_clock_event) + return 0; + + ce = per_cpu_ptr(hv_clock_event, cpu); + ce->name = "Hyper-V clockevent"; + ce->features = CLOCK_EVT_FEAT_ONESHOT; + ce->cpumask = cpumask_of(cpu); + ce->rating = 1000; + ce->set_state_shutdown = hv_ce_shutdown; + ce->set_state_oneshot = hv_ce_set_oneshot; + ce->set_next_event = hv_ce_set_next_event; + + clockevents_config_and_register(ce, + HV_CLOCK_HZ, + HV_MIN_DELTA_TICKS, + HV_MAX_MAX_DELTA_TICKS); + return 0; +} + +/* + * hv_stimer_cleanup - Per-cpu cleanup of the clockevent + */ +int hv_stimer_cleanup(unsigned int cpu) +{ + struct clock_event_device *ce; + + if (!hv_clock_event) + return 0; + + /* + * In the legacy case where Direct Mode is not enabled + * (which can only be on x86/64), stimer cleanup happens + * relatively early in the CPU offlining process. We + * must unbind the stimer-based clockevent device so + * that the LAPIC timer can take over until clockevents + * are no longer needed in the offlining process. Note + * that clockevents_unbind_device() eventually calls + * hv_ce_shutdown(). + * + * The unbind should not be done when Direct Mode is + * enabled because we may be on an architecture where + * there are no other clockevent devices to fallback to. + */ + ce = per_cpu_ptr(hv_clock_event, cpu); + if (direct_mode_enabled) + hv_ce_shutdown(ce); + else + clockevents_unbind_device(ce, cpu); + + return 0; +} +EXPORT_SYMBOL_GPL(hv_stimer_cleanup); + +/* + * These placeholders are overridden by arch specific code on + * architectures that need special setup of the stimer0 IRQ because + * they don't support per-cpu IRQs (such as x86/x64). + */ +void __weak hv_setup_stimer0_handler(void (*handler)(void)) +{ +}; + +void __weak hv_remove_stimer0_handler(void) +{ +}; + +#ifdef CONFIG_ACPI +/* Called only on architectures with per-cpu IRQs (i.e., not x86/x64) */ +static int hv_setup_stimer0_irq(void) +{ + int ret; + + ret = acpi_register_gsi(NULL, HYPERV_STIMER0_VECTOR, + ACPI_EDGE_SENSITIVE, ACPI_ACTIVE_HIGH); + if (ret < 0) { + pr_err("Can't register Hyper-V stimer0 GSI. Error %d", ret); + return ret; + } + stimer0_irq = ret; + + ret = request_percpu_irq(stimer0_irq, hv_stimer0_percpu_isr, + "Hyper-V stimer0", &stimer0_evt); + if (ret) { + pr_err("Can't request Hyper-V stimer0 IRQ %d. Error %d", + stimer0_irq, ret); + acpi_unregister_gsi(stimer0_irq); + stimer0_irq = -1; + } + return ret; +} + +static void hv_remove_stimer0_irq(void) +{ + if (stimer0_irq == -1) { + hv_remove_stimer0_handler(); + } else { + free_percpu_irq(stimer0_irq, &stimer0_evt); + acpi_unregister_gsi(stimer0_irq); + stimer0_irq = -1; + } +} +#else +static int hv_setup_stimer0_irq(void) +{ + return 0; +} + +static void hv_remove_stimer0_irq(void) +{ +} +#endif + +/* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */ +int hv_stimer_alloc(bool have_percpu_irqs) +{ + int ret; + + /* + * Synthetic timers are always available except on old versions of + * Hyper-V on x86. In that case, return as error as Linux will use a + * clockevent based on emulated LAPIC timer hardware. + */ + if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE)) + return -EINVAL; + + hv_clock_event = alloc_percpu(struct clock_event_device); + if (!hv_clock_event) + return -ENOMEM; + + direct_mode_enabled = ms_hyperv.misc_features & + HV_STIMER_DIRECT_MODE_AVAILABLE; + + /* + * If Direct Mode isn't enabled, the remainder of the initialization + * is done later by hv_stimer_legacy_init() + */ + if (!direct_mode_enabled) + return 0; + + if (have_percpu_irqs) { + ret = hv_setup_stimer0_irq(); + if (ret) + goto free_clock_event; + } else { + hv_setup_stimer0_handler(hv_stimer0_isr); + } + + /* + * Since we are in Direct Mode, stimer initialization + * can be done now with a CPUHP value in the same range + * as other clockevent devices. + */ + ret = cpuhp_setup_state(CPUHP_AP_HYPERV_TIMER_STARTING, + "clockevents/hyperv/stimer:starting", + hv_stimer_init, hv_stimer_cleanup); + if (ret < 0) { + hv_remove_stimer0_irq(); + goto free_clock_event; + } + return ret; + +free_clock_event: + free_percpu(hv_clock_event); + hv_clock_event = NULL; + return ret; +} +EXPORT_SYMBOL_GPL(hv_stimer_alloc); + +/* + * hv_stimer_legacy_init -- Called from the VMbus driver to handle + * the case when Direct Mode is not enabled, and the stimer + * must be initialized late in the CPU onlining process. + * + */ +void hv_stimer_legacy_init(unsigned int cpu, int sint) +{ + if (direct_mode_enabled) + return; + + /* + * This function gets called by each vCPU, so setting the + * global stimer_message_sint value each time is conceptually + * not ideal, but the value passed in is always the same and + * it avoids introducing yet another interface into this + * clocksource driver just to set the sint in the legacy case. + */ + stimer0_message_sint = sint; + (void)hv_stimer_init(cpu); +} +EXPORT_SYMBOL_GPL(hv_stimer_legacy_init); + +/* + * hv_stimer_legacy_cleanup -- Called from the VMbus driver to + * handle the case when Direct Mode is not enabled, and the + * stimer must be cleaned up early in the CPU offlining + * process. + */ +void hv_stimer_legacy_cleanup(unsigned int cpu) +{ + if (direct_mode_enabled) + return; + (void)hv_stimer_cleanup(cpu); +} +EXPORT_SYMBOL_GPL(hv_stimer_legacy_cleanup); + +/* + * Do a global cleanup of clockevents for the cases of kexec and + * vmbus exit + */ +void hv_stimer_global_cleanup(void) +{ + int cpu; + + /* + * hv_stime_legacy_cleanup() will stop the stimer if Direct + * Mode is not enabled, and fallback to the LAPIC timer. + */ + for_each_present_cpu(cpu) { + hv_stimer_legacy_cleanup(cpu); + } + + if (!hv_clock_event) + return; + + if (direct_mode_enabled) { + cpuhp_remove_state(CPUHP_AP_HYPERV_TIMER_STARTING); + hv_remove_stimer0_irq(); + stimer0_irq = -1; + } + free_percpu(hv_clock_event); + hv_clock_event = NULL; + +} +EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup); + +static __always_inline u64 read_hv_clock_msr(void) +{ + /* + * Read the partition counter to get the current tick count. This count + * is set to 0 when the partition is created and is incremented in 100 + * nanosecond units. + * + * Use hv_raw_get_register() because this function is used from + * noinstr. Notable; while HV_REGISTER_TIME_REF_COUNT is a synthetic + * register it doesn't need the GHCB path. + */ + return hv_raw_get_register(HV_REGISTER_TIME_REF_COUNT); +} + +/* + * Code and definitions for the Hyper-V clocksources. Two + * clocksources are defined: one that reads the Hyper-V defined MSR, and + * the other that uses the TSC reference page feature as defined in the + * TLFS. The MSR version is for compatibility with old versions of + * Hyper-V and 32-bit x86. The TSC reference page version is preferred. + */ + +static union { + struct ms_hyperv_tsc_page page; + u8 reserved[PAGE_SIZE]; +} tsc_pg __bss_decrypted __aligned(PAGE_SIZE); + +static struct ms_hyperv_tsc_page *tsc_page = &tsc_pg.page; +static unsigned long tsc_pfn; + +unsigned long hv_get_tsc_pfn(void) +{ + return tsc_pfn; +} +EXPORT_SYMBOL_GPL(hv_get_tsc_pfn); + +struct ms_hyperv_tsc_page *hv_get_tsc_page(void) +{ + return tsc_page; +} +EXPORT_SYMBOL_GPL(hv_get_tsc_page); + +static __always_inline u64 read_hv_clock_tsc(void) +{ + u64 cur_tsc, time; + + /* + * The Hyper-V Top-Level Function Spec (TLFS), section Timers, + * subsection Refererence Counter, guarantees that the TSC and MSR + * times are in sync and monotonic. Therefore we can fall back + * to the MSR in case the TSC page indicates unavailability. + */ + if (!hv_read_tsc_page_tsc(tsc_page, &cur_tsc, &time)) + time = read_hv_clock_msr(); + + return time; +} + +static u64 notrace read_hv_clock_tsc_cs(struct clocksource *arg) +{ + return read_hv_clock_tsc(); +} + +static u64 noinstr read_hv_sched_clock_tsc(void) +{ + return (read_hv_clock_tsc() - hv_sched_clock_offset) * + (NSEC_PER_SEC / HV_CLOCK_HZ); +} + +static void suspend_hv_clock_tsc(struct clocksource *arg) +{ + union hv_reference_tsc_msr tsc_msr; + + /* Disable the TSC page */ + tsc_msr.as_uint64 = hv_get_register(HV_REGISTER_REFERENCE_TSC); + tsc_msr.enable = 0; + hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr.as_uint64); +} + + +static void resume_hv_clock_tsc(struct clocksource *arg) +{ + union hv_reference_tsc_msr tsc_msr; + + /* Re-enable the TSC page */ + tsc_msr.as_uint64 = hv_get_register(HV_REGISTER_REFERENCE_TSC); + tsc_msr.enable = 1; + tsc_msr.pfn = tsc_pfn; + hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr.as_uint64); +} + +#ifdef HAVE_VDSO_CLOCKMODE_HVCLOCK +static int hv_cs_enable(struct clocksource *cs) +{ + vclocks_set_used(VDSO_CLOCKMODE_HVCLOCK); + return 0; +} +#endif + +static struct clocksource hyperv_cs_tsc = { + .name = "hyperv_clocksource_tsc_page", + .rating = 500, + .read = read_hv_clock_tsc_cs, + .mask = CLOCKSOURCE_MASK(64), + .flags = CLOCK_SOURCE_IS_CONTINUOUS, + .suspend= suspend_hv_clock_tsc, + .resume = resume_hv_clock_tsc, +#ifdef HAVE_VDSO_CLOCKMODE_HVCLOCK + .enable = hv_cs_enable, + .vdso_clock_mode = VDSO_CLOCKMODE_HVCLOCK, +#else + .vdso_clock_mode = VDSO_CLOCKMODE_NONE, +#endif +}; + +static u64 notrace read_hv_clock_msr_cs(struct clocksource *arg) +{ + return read_hv_clock_msr(); +} + +static struct clocksource hyperv_cs_msr = { + .name = "hyperv_clocksource_msr", + .rating = 495, + .read = read_hv_clock_msr_cs, + .mask = CLOCKSOURCE_MASK(64), + .flags = CLOCK_SOURCE_IS_CONTINUOUS, +}; + +/* + * Reference to pv_ops must be inline so objtool + * detection of noinstr violations can work correctly. + */ +#ifdef CONFIG_GENERIC_SCHED_CLOCK +static __always_inline void hv_setup_sched_clock(void *sched_clock) +{ + /* + * We're on an architecture with generic sched clock (not x86/x64). + * The Hyper-V sched clock read function returns nanoseconds, not + * the normal 100ns units of the Hyper-V synthetic clock. + */ + sched_clock_register(sched_clock, 64, NSEC_PER_SEC); +} +#elif defined CONFIG_PARAVIRT +static __always_inline void hv_setup_sched_clock(void *sched_clock) +{ + /* We're on x86/x64 *and* using PV ops */ + paravirt_set_sched_clock(sched_clock); +} +#else /* !CONFIG_GENERIC_SCHED_CLOCK && !CONFIG_PARAVIRT */ +static __always_inline void hv_setup_sched_clock(void *sched_clock) {} +#endif /* CONFIG_GENERIC_SCHED_CLOCK */ + +static void __init hv_init_tsc_clocksource(void) +{ + union hv_reference_tsc_msr tsc_msr; + + /* + * If Hyper-V offers TSC_INVARIANT, then the virtualized TSC correctly + * handles frequency and offset changes due to live migration, + * pause/resume, and other VM management operations. So lower the + * Hyper-V Reference TSC rating, causing the generic TSC to be used. + * TSC_INVARIANT is not offered on ARM64, so the Hyper-V Reference + * TSC will be preferred over the virtualized ARM64 arch counter. + */ + if (ms_hyperv.features & HV_ACCESS_TSC_INVARIANT) { + hyperv_cs_tsc.rating = 250; + hyperv_cs_msr.rating = 245; + } + + if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE)) + return; + + hv_read_reference_counter = read_hv_clock_tsc; + + /* + * TSC page mapping works differently in root compared to guest. + * - In guest partition the guest PFN has to be passed to the + * hypervisor. + * - In root partition it's other way around: it has to map the PFN + * provided by the hypervisor. + * But it can't be mapped right here as it's too early and MMU isn't + * ready yet. So, we only set the enable bit here and will remap the + * page later in hv_remap_tsc_clocksource(). + * + * It worth mentioning, that TSC clocksource read function + * (read_hv_clock_tsc) has a MSR-based fallback mechanism, used when + * TSC page is zeroed (which is the case until the PFN is remapped) and + * thus TSC clocksource will work even without the real TSC page + * mapped. + */ + tsc_msr.as_uint64 = hv_get_register(HV_REGISTER_REFERENCE_TSC); + if (hv_root_partition) + tsc_pfn = tsc_msr.pfn; + else + tsc_pfn = HVPFN_DOWN(virt_to_phys(tsc_page)); + tsc_msr.enable = 1; + tsc_msr.pfn = tsc_pfn; + hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr.as_uint64); + + clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100); + + /* + * If TSC is invariant, then let it stay as the sched clock since it + * will be faster than reading the TSC page. But if not invariant, use + * the TSC page so that live migrations across hosts with different + * frequencies is handled correctly. + */ + if (!(ms_hyperv.features & HV_ACCESS_TSC_INVARIANT)) { + hv_sched_clock_offset = hv_read_reference_counter(); + hv_setup_sched_clock(read_hv_sched_clock_tsc); + } +} + +void __init hv_init_clocksource(void) +{ + /* + * Try to set up the TSC page clocksource, then the MSR clocksource. + * At least one of these will always be available except on very old + * versions of Hyper-V on x86. In that case we won't have a Hyper-V + * clocksource, but Linux will still run with a clocksource based + * on the emulated PIT or LAPIC timer. + * + * Never use the MSR clocksource as sched clock. It's too slow. + * Better to use the native sched clock as the fallback. + */ + hv_init_tsc_clocksource(); + + if (ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE) + clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100); +} + +void __init hv_remap_tsc_clocksource(void) +{ + if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE)) + return; + + if (!hv_root_partition) { + WARN(1, "%s: attempt to remap TSC page in guest partition\n", + __func__); + return; + } + + tsc_page = memremap(tsc_pfn << HV_HYP_PAGE_SHIFT, sizeof(tsc_pg), + MEMREMAP_WB); + if (!tsc_page) + pr_err("Failed to remap Hyper-V TSC page.\n"); +} |