From 450bbd493d436f9eadd1b7828158f37559f26674 Mon Sep 17 00:00:00 2001 From: Robert Richter Date: Mon, 12 Mar 2012 12:54:32 +0100 Subject: [PATCH] perf/x86-ibs: Precise event sampling with IBS for AMD CPUs This patch adds support for precise event sampling with IBS. There are two counting modes to count either cycles or micro-ops. If the corresponding performance counter events (hw events) are setup with the precise flag set, the request is redirected to the ibs pmu: perf record -a -e cpu-cycles:p ... # use ibs op counting cycle count perf record -a -e r076:p ... # same as -e cpu-cycles:p perf record -a -e r0C1:p ... # use ibs op counting micro-ops Each ibs sample contains a linear address that points to the instruction that was causing the sample to trigger. With ibs we have skid 0. Thus, ibs supports precise levels 1 and 2. Samples are marked with the PERF_EFLAGS_EXACT flag set. In rare cases the rip is invalid when IBS was not able to record the rip correctly. Then the PERF_EFLAGS_EXACT flag is cleared and the rip is taken from pt_regs. V2: * don't drop samples in precise level 2 if rip is invalid, instead support the PERF_EFLAGS_EXACT flag Signed-off-by: Robert Richter Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/20120502103309.GP18810@erda.amd.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event_amd.c | 7 ++- arch/x86/kernel/cpu/perf_event_amd_ibs.c | 73 +++++++++++++++++++++++- 2 files changed, 76 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_amd.c b/arch/x86/kernel/cpu/perf_event_amd.c index 589286f2887..65652265fff 100644 --- a/arch/x86/kernel/cpu/perf_event_amd.c +++ b/arch/x86/kernel/cpu/perf_event_amd.c @@ -134,8 +134,13 @@ static u64 amd_pmu_event_map(int hw_event) static int amd_pmu_hw_config(struct perf_event *event) { - int ret = x86_pmu_hw_config(event); + int ret; + /* pass precise event sampling to ibs: */ + if (event->attr.precise_ip && get_ibs_caps()) + return -ENOENT; + + ret = x86_pmu_hw_config(event); if (ret) return ret; diff --git a/arch/x86/kernel/cpu/perf_event_amd_ibs.c b/arch/x86/kernel/cpu/perf_event_amd_ibs.c index cc1f3293d6c..34dfa853f6d 100644 --- a/arch/x86/kernel/cpu/perf_event_amd_ibs.c +++ b/arch/x86/kernel/cpu/perf_event_amd_ibs.c @@ -145,17 +145,80 @@ static struct perf_ibs *get_ibs_pmu(int type) return NULL; } +/* + * Use IBS for precise event sampling: + * + * perf record -a -e cpu-cycles:p ... # use ibs op counting cycle count + * perf record -a -e r076:p ... # same as -e cpu-cycles:p + * perf record -a -e r0C1:p ... # use ibs op counting micro-ops + * + * IbsOpCntCtl (bit 19) of IBS Execution Control Register (IbsOpCtl, + * MSRC001_1033) is used to select either cycle or micro-ops counting + * mode. + * + * The rip of IBS samples has skid 0. Thus, IBS supports precise + * levels 1 and 2 and the PERF_EFLAGS_EXACT is set. In rare cases the + * rip is invalid when IBS was not able to record the rip correctly. + * We clear PERF_EFLAGS_EXACT and take the rip from pt_regs then. + * + */ +static int perf_ibs_precise_event(struct perf_event *event, u64 *config) +{ + switch (event->attr.precise_ip) { + case 0: + return -ENOENT; + case 1: + case 2: + break; + default: + return -EOPNOTSUPP; + } + + switch (event->attr.type) { + case PERF_TYPE_HARDWARE: + switch (event->attr.config) { + case PERF_COUNT_HW_CPU_CYCLES: + *config = 0; + return 0; + } + break; + case PERF_TYPE_RAW: + switch (event->attr.config) { + case 0x0076: + *config = 0; + return 0; + case 0x00C1: + *config = IBS_OP_CNT_CTL; + return 0; + } + break; + default: + return -ENOENT; + } + + return -EOPNOTSUPP; +} + static int perf_ibs_init(struct perf_event *event) { struct hw_perf_event *hwc = &event->hw; struct perf_ibs *perf_ibs; u64 max_cnt, config; + int ret; perf_ibs = get_ibs_pmu(event->attr.type); - if (!perf_ibs) + if (perf_ibs) { + config = event->attr.config; + } else { + perf_ibs = &perf_ibs_op; + ret = perf_ibs_precise_event(event, &config); + if (ret) + return ret; + } + + if (event->pmu != &perf_ibs->pmu) return -ENOENT; - config = event->attr.config; if (config & ~perf_ibs->config_mask) return -EINVAL; @@ -437,8 +500,12 @@ static int perf_ibs_handle_irq(struct perf_ibs *perf_ibs, struct pt_regs *iregs) ibs_data.size = sizeof(u64) * size; regs = *iregs; - if (!check_rip || !(ibs_data.regs[2] & IBS_RIP_INVALID)) + if (check_rip && (ibs_data.regs[2] & IBS_RIP_INVALID)) { + regs.flags &= ~PERF_EFLAGS_EXACT; + } else { instruction_pointer_set(®s, ibs_data.regs[1]); + regs.flags |= PERF_EFLAGS_EXACT; + } if (event->attr.sample_type & PERF_SAMPLE_RAW) { raw.size = sizeof(u32) + ibs_data.size; -- 2.20.1