diff options
Diffstat (limited to 'arch/x86/events/amd/core.c')
| -rw-r--r-- | arch/x86/events/amd/core.c | 140 |
1 files changed, 135 insertions, 5 deletions
diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c index 7d2d7c801dba..0ecfac84ba91 100644 --- a/arch/x86/events/amd/core.c +++ b/arch/x86/events/amd/core.c @@ -3,10 +3,14 @@ #include <linux/types.h> #include <linux/init.h> #include <linux/slab.h> +#include <linux/delay.h> #include <asm/apicdef.h> +#include <asm/nmi.h> #include "../perf_event.h" +static DEFINE_PER_CPU(unsigned int, perf_nmi_counter); + static __initconst const u64 amd_hw_cache_event_ids [PERF_COUNT_HW_CACHE_MAX] [PERF_COUNT_HW_CACHE_OP_MAX] @@ -429,6 +433,132 @@ static void amd_pmu_cpu_dead(int cpu) } } +/* + * When a PMC counter overflows, an NMI is used to process the event and + * reset the counter. NMI latency can result in the counter being updated + * before the NMI can run, which can result in what appear to be spurious + * NMIs. This function is intended to wait for the NMI to run and reset + * the counter to avoid possible unhandled NMI messages. + */ +#define OVERFLOW_WAIT_COUNT 50 + +static void amd_pmu_wait_on_overflow(int idx) +{ + unsigned int i; + u64 counter; + + /* + * Wait for the counter to be reset if it has overflowed. This loop + * should exit very, very quickly, but just in case, don't wait + * forever... + */ + for (i = 0; i < OVERFLOW_WAIT_COUNT; i++) { + rdmsrl(x86_pmu_event_addr(idx), counter); + if (counter & (1ULL << (x86_pmu.cntval_bits - 1))) + break; + + /* Might be in IRQ context, so can't sleep */ + udelay(1); + } +} + +static void amd_pmu_disable_all(void) +{ + struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); + int idx; + + x86_pmu_disable_all(); + + /* + * This shouldn't be called from NMI context, but add a safeguard here + * to return, since if we're in NMI context we can't wait for an NMI + * to reset an overflowed counter value. + */ + if (in_nmi()) + return; + + /* + * Check each counter for overflow and wait for it to be reset by the + * NMI if it has overflowed. This relies on the fact that all active + * counters are always enabled when this function is caled and + * ARCH_PERFMON_EVENTSEL_INT is always set. + */ + for (idx = 0; idx < x86_pmu.num_counters; idx++) { + if (!test_bit(idx, cpuc->active_mask)) + continue; + + amd_pmu_wait_on_overflow(idx); + } +} + +static void amd_pmu_disable_event(struct perf_event *event) +{ + x86_pmu_disable_event(event); + + /* + * This can be called from NMI context (via x86_pmu_stop). The counter + * may have overflowed, but either way, we'll never see it get reset + * by the NMI if we're already in the NMI. And the NMI latency support + * below will take care of any pending NMI that might have been + * generated by the overflow. + */ + if (in_nmi()) + return; + + amd_pmu_wait_on_overflow(event->hw.idx); +} + +/* + * Because of NMI latency, if multiple PMC counters are active or other sources + * of NMIs are received, the perf NMI handler can handle one or more overflowed + * PMC counters outside of the NMI associated with the PMC overflow. If the NMI + * doesn't arrive at the LAPIC in time to become a pending NMI, then the kernel + * back-to-back NMI support won't be active. This PMC handler needs to take into + * account that this can occur, otherwise this could result in unknown NMI + * messages being issued. Examples of this is PMC overflow while in the NMI + * handler when multiple PMCs are active or PMC overflow while handling some + * other source of an NMI. + * + * Attempt to mitigate this by using the number of active PMCs to determine + * whether to return NMI_HANDLED if the perf NMI handler did not handle/reset + * any PMCs. The per-CPU perf_nmi_counter variable is set to a minimum of the + * number of active PMCs or 2. The value of 2 is used in case an NMI does not + * arrive at the LAPIC in time to be collapsed into an already pending NMI. + */ +static int amd_pmu_handle_irq(struct pt_regs *regs) +{ + struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); + int active, handled; + + /* + * Obtain the active count before calling x86_pmu_handle_irq() since + * it is possible that x86_pmu_handle_irq() may make a counter + * inactive (through x86_pmu_stop). + */ + active = __bitmap_weight(cpuc->active_mask, X86_PMC_IDX_MAX); + + /* Process any counter overflows */ + handled = x86_pmu_handle_irq(regs); + + /* + * If a counter was handled, record the number of possible remaining + * NMIs that can occur. + */ + if (handled) { + this_cpu_write(perf_nmi_counter, + min_t(unsigned int, 2, active)); + + return handled; + } + + if (!this_cpu_read(perf_nmi_counter)) + return NMI_DONE; + + this_cpu_dec(perf_nmi_counter); + + return NMI_HANDLED; +} + static struct event_constraint * amd_get_event_constraints(struct cpu_hw_events *cpuc, int idx, struct perf_event *event) @@ -621,11 +751,11 @@ static ssize_t amd_event_sysfs_show(char *page, u64 config) static __initconst const struct x86_pmu amd_pmu = { .name = "AMD", - .handle_irq = x86_pmu_handle_irq, - .disable_all = x86_pmu_disable_all, + .handle_irq = amd_pmu_handle_irq, + .disable_all = amd_pmu_disable_all, .enable_all = x86_pmu_enable_all, .enable = x86_pmu_enable_event, - .disable = x86_pmu_disable_event, + .disable = amd_pmu_disable_event, .hw_config = amd_pmu_hw_config, .schedule_events = x86_schedule_events, .eventsel = MSR_K7_EVNTSEL0, @@ -732,7 +862,7 @@ void amd_pmu_enable_virt(void) cpuc->perf_ctr_virt_mask = 0; /* Reload all events */ - x86_pmu_disable_all(); + amd_pmu_disable_all(); x86_pmu_enable_all(0); } EXPORT_SYMBOL_GPL(amd_pmu_enable_virt); @@ -750,7 +880,7 @@ void amd_pmu_disable_virt(void) cpuc->perf_ctr_virt_mask = AMD64_EVENTSEL_HOSTONLY; /* Reload all events */ - x86_pmu_disable_all(); + amd_pmu_disable_all(); x86_pmu_enable_all(0); } EXPORT_SYMBOL_GPL(amd_pmu_disable_virt); |