diff options
Diffstat (limited to 'arch/x86/xen/time.c')
| -rw-r--r-- | arch/x86/xen/time.c | 593 |
1 files changed, 593 insertions, 0 deletions
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c new file mode 100644 index 00000000000..dfd6db69ead --- /dev/null +++ b/arch/x86/xen/time.c @@ -0,0 +1,593 @@ +/* + * Xen time implementation. + * + * This is implemented in terms of a clocksource driver which uses + * the hypervisor clock as a nanosecond timebase, and a clockevent + * driver which uses the hypervisor's timer mechanism. + * + * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007 + */ +#include <linux/kernel.h> +#include <linux/interrupt.h> +#include <linux/clocksource.h> +#include <linux/clockchips.h> +#include <linux/kernel_stat.h> + +#include <asm/xen/hypervisor.h> +#include <asm/xen/hypercall.h> + +#include <xen/events.h> +#include <xen/interface/xen.h> +#include <xen/interface/vcpu.h> + +#include "xen-ops.h" + +#define XEN_SHIFT 22 + +/* Xen may fire a timer up to this many ns early */ +#define TIMER_SLOP 100000 +#define NS_PER_TICK (1000000000LL / HZ) + +static cycle_t xen_clocksource_read(void); + +/* These are perodically updated in shared_info, and then copied here. */ +struct shadow_time_info { + u64 tsc_timestamp; /* TSC at last update of time vals. */ + u64 system_timestamp; /* Time, in nanosecs, since boot. */ + u32 tsc_to_nsec_mul; + int tsc_shift; + u32 version; +}; + +static DEFINE_PER_CPU(struct shadow_time_info, shadow_time); + +/* runstate info updated by Xen */ +static DEFINE_PER_CPU(struct vcpu_runstate_info, runstate); + +/* snapshots of runstate info */ +static DEFINE_PER_CPU(struct vcpu_runstate_info, runstate_snapshot); + +/* unused ns of stolen and blocked time */ +static DEFINE_PER_CPU(u64, residual_stolen); +static DEFINE_PER_CPU(u64, residual_blocked); + +/* return an consistent snapshot of 64-bit time/counter value */ +static u64 get64(const u64 *p) +{ + u64 ret; + + if (BITS_PER_LONG < 64) { + u32 *p32 = (u32 *)p; + u32 h, l; + + /* + * Read high then low, and then make sure high is + * still the same; this will only loop if low wraps + * and carries into high. + * XXX some clean way to make this endian-proof? + */ + do { + h = p32[1]; + barrier(); + l = p32[0]; + barrier(); + } while (p32[1] != h); + + ret = (((u64)h) << 32) | l; + } else + ret = *p; + + return ret; +} + +/* + * Runstate accounting + */ +static void get_runstate_snapshot(struct vcpu_runstate_info *res) +{ + u64 state_time; + struct vcpu_runstate_info *state; + + BUG_ON(preemptible()); + + state = &__get_cpu_var(runstate); + + /* + * The runstate info is always updated by the hypervisor on + * the current CPU, so there's no need to use anything + * stronger than a compiler barrier when fetching it. + */ + do { + state_time = get64(&state->state_entry_time); + barrier(); + *res = *state; + barrier(); + } while (get64(&state->state_entry_time) != state_time); +} + +static void setup_runstate_info(int cpu) +{ + struct vcpu_register_runstate_memory_area area; + + area.addr.v = &per_cpu(runstate, cpu); + + if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area, + cpu, &area)) + BUG(); +} + +static void do_stolen_accounting(void) +{ + struct vcpu_runstate_info state; + struct vcpu_runstate_info *snap; + s64 blocked, runnable, offline, stolen; + cputime_t ticks; + + get_runstate_snapshot(&state); + + WARN_ON(state.state != RUNSTATE_running); + + snap = &__get_cpu_var(runstate_snapshot); + + /* work out how much time the VCPU has not been runn*ing* */ + blocked = state.time[RUNSTATE_blocked] - snap->time[RUNSTATE_blocked]; + runnable = state.time[RUNSTATE_runnable] - snap->time[RUNSTATE_runnable]; + offline = state.time[RUNSTATE_offline] - snap->time[RUNSTATE_offline]; + + *snap = state; + + /* Add the appropriate number of ticks of stolen time, + including any left-overs from last time. Passing NULL to + account_steal_time accounts the time as stolen. */ + stolen = runnable + offline + __get_cpu_var(residual_stolen); + + if (stolen < 0) + stolen = 0; + + ticks = 0; + while (stolen >= NS_PER_TICK) { + ticks++; + stolen -= NS_PER_TICK; + } + __get_cpu_var(residual_stolen) = stolen; + account_steal_time(NULL, ticks); + + /* Add the appropriate number of ticks of blocked time, + including any left-overs from last time. Passing idle to + account_steal_time accounts the time as idle/wait. */ + blocked += __get_cpu_var(residual_blocked); + + if (blocked < 0) + blocked = 0; + + ticks = 0; + while (blocked >= NS_PER_TICK) { + ticks++; + blocked -= NS_PER_TICK; + } + __get_cpu_var(residual_blocked) = blocked; + account_steal_time(idle_task(smp_processor_id()), ticks); +} + +/* + * Xen sched_clock implementation. Returns the number of unstolen + * nanoseconds, which is nanoseconds the VCPU spent in RUNNING+BLOCKED + * states. + */ +unsigned long long xen_sched_clock(void) +{ + struct vcpu_runstate_info state; + cycle_t now; + u64 ret; + s64 offset; + + /* + * Ideally sched_clock should be called on a per-cpu basis + * anyway, so preempt should already be disabled, but that's + * not current practice at the moment. + */ + preempt_disable(); + + now = xen_clocksource_read(); + + get_runstate_snapshot(&state); + + WARN_ON(state.state != RUNSTATE_running); + + offset = now - state.state_entry_time; + if (offset < 0) + offset = 0; + + ret = state.time[RUNSTATE_blocked] + + state.time[RUNSTATE_running] + + offset; + + preempt_enable(); + + return ret; +} + + +/* Get the CPU speed from Xen */ +unsigned long xen_cpu_khz(void) +{ + u64 cpu_khz = 1000000ULL << 32; + const struct vcpu_time_info *info = + &HYPERVISOR_shared_info->vcpu_info[0].time; + + do_div(cpu_khz, info->tsc_to_system_mul); + if (info->tsc_shift < 0) + cpu_khz <<= -info->tsc_shift; + else + cpu_khz >>= info->tsc_shift; + + return cpu_khz; +} + +/* + * Reads a consistent set of time-base values from Xen, into a shadow data + * area. + */ +static unsigned get_time_values_from_xen(void) +{ + struct vcpu_time_info *src; + struct shadow_time_info *dst; + + /* src is shared memory with the hypervisor, so we need to + make sure we get a consistent snapshot, even in the face of + being preempted. */ + src = &__get_cpu_var(xen_vcpu)->time; + dst = &__get_cpu_var(shadow_time); + + do { + dst->version = src->version; + rmb(); /* fetch version before data */ + dst->tsc_timestamp = src->tsc_timestamp; + dst->system_timestamp = src->system_time; + dst->tsc_to_nsec_mul = src->tsc_to_system_mul; + dst->tsc_shift = src->tsc_shift; + rmb(); /* test version after fetching data */ + } while ((src->version & 1) | (dst->version ^ src->version)); + + return dst->version; +} + +/* + * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction, + * yielding a 64-bit result. + */ +static inline u64 scale_delta(u64 delta, u32 mul_frac, int shift) +{ + u64 product; +#ifdef __i386__ + u32 tmp1, tmp2; +#endif + + if (shift < 0) + delta >>= -shift; + else + delta <<= shift; + +#ifdef __i386__ + __asm__ ( + "mul %5 ; " + "mov %4,%%eax ; " + "mov %%edx,%4 ; " + "mul %5 ; " + "xor %5,%5 ; " + "add %4,%%eax ; " + "adc %5,%%edx ; " + : "=A" (product), "=r" (tmp1), "=r" (tmp2) + : "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) ); +#elif __x86_64__ + __asm__ ( + "mul %%rdx ; shrd $32,%%rdx,%%rax" + : "=a" (product) : "0" (delta), "d" ((u64)mul_frac) ); +#else +#error implement me! +#endif + + return product; +} + +static u64 get_nsec_offset(struct shadow_time_info *shadow) +{ + u64 now, delta; + now = native_read_tsc(); + delta = now - shadow->tsc_timestamp; + return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift); +} + +static cycle_t xen_clocksource_read(void) +{ + struct shadow_time_info *shadow = &get_cpu_var(shadow_time); + cycle_t ret; + unsigned version; + + do { + version = get_time_values_from_xen(); + barrier(); + ret = shadow->system_timestamp + get_nsec_offset(shadow); + barrier(); + } while (version != __get_cpu_var(xen_vcpu)->time.version); + + put_cpu_var(shadow_time); + + return ret; +} + +static void xen_read_wallclock(struct timespec *ts) +{ + const struct shared_info *s = HYPERVISOR_shared_info; + u32 version; + u64 delta; + struct timespec now; + + /* get wallclock at system boot */ + do { + version = s->wc_version; + rmb(); /* fetch version before time */ + now.tv_sec = s->wc_sec; + now.tv_nsec = s->wc_nsec; + rmb(); /* fetch time before checking version */ + } while ((s->wc_version & 1) | (version ^ s->wc_version)); + + delta = xen_clocksource_read(); /* time since system boot */ + delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec; + + now.tv_nsec = do_div(delta, NSEC_PER_SEC); + now.tv_sec = delta; + + set_normalized_timespec(ts, now.tv_sec, now.tv_nsec); +} + +unsigned long xen_get_wallclock(void) +{ + struct timespec ts; + + xen_read_wallclock(&ts); + + return ts.tv_sec; +} + +int xen_set_wallclock(unsigned long now) +{ + /* do nothing for domU */ + return -1; +} + +static struct clocksource xen_clocksource __read_mostly = { + .name = "xen", + .rating = 400, + .read = xen_clocksource_read, + .mask = ~0, + .mult = 1<<XEN_SHIFT, /* time directly in nanoseconds */ + .shift = XEN_SHIFT, + .flags = CLOCK_SOURCE_IS_CONTINUOUS, +}; + +/* + Xen clockevent implementation + + Xen has two clockevent implementations: + + The old timer_op one works with all released versions of Xen prior + to version 3.0.4. This version of the hypervisor provides a + single-shot timer with nanosecond resolution. However, sharing the + same event channel is a 100Hz tick which is delivered while the + vcpu is running. We don't care about or use this tick, but it will + cause the core time code to think the timer fired too soon, and + will end up resetting it each time. It could be filtered, but + doing so has complications when the ktime clocksource is not yet + the xen clocksource (ie, at boot time). + + The new vcpu_op-based timer interface allows the tick timer period + to be changed or turned off. The tick timer is not useful as a + periodic timer because events are only delivered to running vcpus. + The one-shot timer can report when a timeout is in the past, so + set_next_event is capable of returning -ETIME when appropriate. + This interface is used when available. +*/ + + +/* + Get a hypervisor absolute time. In theory we could maintain an + offset between the kernel's time and the hypervisor's time, and + apply that to a kernel's absolute timeout. Unfortunately the + hypervisor and kernel times can drift even if the kernel is using + the Xen clocksource, because ntp can warp the kernel's clocksource. +*/ +static s64 get_abs_timeout(unsigned long delta) +{ + return xen_clocksource_read() + delta; +} + +static void xen_timerop_set_mode(enum clock_event_mode mode, + struct clock_event_device *evt) +{ + switch (mode) { + case CLOCK_EVT_MODE_PERIODIC: + /* unsupported */ + WARN_ON(1); + break; + + case CLOCK_EVT_MODE_ONESHOT: + case CLOCK_EVT_MODE_RESUME: + break; + + case CLOCK_EVT_MODE_UNUSED: + case CLOCK_EVT_MODE_SHUTDOWN: + HYPERVISOR_set_timer_op(0); /* cancel timeout */ + break; + } +} + +static int xen_timerop_set_next_event(unsigned long delta, + struct clock_event_device *evt) +{ + WARN_ON(evt->mode != CLOCK_EVT_MODE_ONESHOT); + + if (HYPERVISOR_set_timer_op(get_abs_timeout(delta)) < 0) + BUG(); + + /* We may have missed the deadline, but there's no real way of + knowing for sure. If the event was in the past, then we'll + get an immediate interrupt. */ + + return 0; +} + +static const struct clock_event_device xen_timerop_clockevent = { + .name = "xen", + .features = CLOCK_EVT_FEAT_ONESHOT, + + .max_delta_ns = 0xffffffff, + .min_delta_ns = TIMER_SLOP, + + .mult = 1, + .shift = 0, + .rating = 500, + + .set_mode = xen_timerop_set_mode, + .set_next_event = xen_timerop_set_next_event, +}; + + + +static void xen_vcpuop_set_mode(enum clock_event_mode mode, + struct clock_event_device *evt) +{ + int cpu = smp_processor_id(); + + switch (mode) { + case CLOCK_EVT_MODE_PERIODIC: + WARN_ON(1); /* unsupported */ + break; + + case CLOCK_EVT_MODE_ONESHOT: + if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL)) + BUG(); + break; + + case CLOCK_EVT_MODE_UNUSED: + case CLOCK_EVT_MODE_SHUTDOWN: + if (HYPERVISOR_vcpu_op(VCPUOP_stop_singleshot_timer, cpu, NULL) || + HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL)) + BUG(); + break; + case CLOCK_EVT_MODE_RESUME: + break; + } +} + +static int xen_vcpuop_set_next_event(unsigned long delta, + struct clock_event_device *evt) +{ + int cpu = smp_processor_id(); + struct vcpu_set_singleshot_timer single; + int ret; + + WARN_ON(evt->mode != CLOCK_EVT_MODE_ONESHOT); + + single.timeout_abs_ns = get_abs_timeout(delta); + single.flags = VCPU_SSHOTTMR_future; + + ret = HYPERVISOR_vcpu_op(VCPUOP_set_singleshot_timer, cpu, &single); + + BUG_ON(ret != 0 && ret != -ETIME); + + return ret; +} + +static const struct clock_event_device xen_vcpuop_clockevent = { + .name = "xen", + .features = CLOCK_EVT_FEAT_ONESHOT, + + .max_delta_ns = 0xffffffff, + .min_delta_ns = TIMER_SLOP, + + .mult = 1, + .shift = 0, + .rating = 500, + + .set_mode = xen_vcpuop_set_mode, + .set_next_event = xen_vcpuop_set_next_event, +}; + +static const struct clock_event_device *xen_clockevent = + &xen_timerop_clockevent; +static DEFINE_PER_CPU(struct clock_event_device, xen_clock_events); + +static irqreturn_t xen_timer_interrupt(int irq, void *dev_id) +{ + struct clock_event_device *evt = &__get_cpu_var(xen_clock_events); + irqreturn_t ret; + + ret = IRQ_NONE; + if (evt->event_handler) { + evt->event_handler(evt); + ret = IRQ_HANDLED; + } + + do_stolen_accounting(); + + return ret; +} + +void xen_setup_timer(int cpu) +{ + const char *name; + struct clock_event_device *evt; + int irq; + + printk(KERN_INFO "installing Xen timer for CPU %d\n", cpu); + + name = kasprintf(GFP_KERNEL, "timer%d", cpu); + if (!name) + name = "<timer kasprintf failed>"; + + irq = bind_virq_to_irqhandler(VIRQ_TIMER, cpu, xen_timer_interrupt, + IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING, + name, NULL); + + evt = &per_cpu(xen_clock_events, cpu); + memcpy(evt, xen_clockevent, sizeof(*evt)); + + evt->cpumask = cpumask_of_cpu(cpu); + evt->irq = irq; + + setup_runstate_info(cpu); +} + +void xen_setup_cpu_clockevents(void) +{ + BUG_ON(preemptible()); + + clockevents_register_device(&__get_cpu_var(xen_clock_events)); +} + +__init void xen_time_init(void) +{ + int cpu = smp_processor_id(); + + get_time_values_from_xen(); + + clocksource_register(&xen_clocksource); + + if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) { + /* Successfully turned off 100Hz tick, so we have the + vcpuop-based timer interface */ + printk(KERN_DEBUG "Xen: using vcpuop timer interface\n"); + xen_clockevent = &xen_vcpuop_clockevent; + } + + /* Set initial system time with full resolution */ + xen_read_wallclock(&xtime); + set_normalized_timespec(&wall_to_monotonic, + -xtime.tv_sec, -xtime.tv_nsec); + + tsc_disable = 0; + + xen_setup_timer(cpu); + xen_setup_cpu_clockevents(); +} |