From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756519AbdLTToG (ORCPT ); Wed, 20 Dec 2017 14:44:06 -0500 Received: from mga07.intel.com ([134.134.136.100]:25387 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755904AbdLTTnu (ORCPT ); Wed, 20 Dec 2017 14:43:50 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.45,433,1508828400"; d="scan'208";a="3499123" From: kan.liang@linux.intel.com To: peterz@infradead.org, mingo@redhat.com, acme@kernel.org, linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, jolsa@redhat.com, eranian@google.com, ak@linux.intel.com, Kan Liang Subject: [PATCH V2 0/4] bug fix mmap read and rdpmc read in large PEBS Date: Wed, 20 Dec 2017 11:42:47 -0800 Message-Id: <1513798971-4257-1-git-send-email-kan.liang@linux.intel.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kan Liang ------ Changes since V1: - Check PERF_X86_EVENT_AUTO_RELOAD before call intel_pmu_save_and_restore() - Introduce a special purpose intel_pmu_save_and_restart() just for AUTO_RELOAD. - New patch to disable userspace RDPMC usage if large PEBS is enabled. ------ There is bug when mmap read event->count with large PEBS enabled. Here is an example. #./read_count 0x71f0 0x122c0 0x1000000001c54 0x100000001257d 0x200000000bdc5 The bug is caused by two issues. - In x86_perf_event_update, the calculation of event->count does not take the auto-reload values into account. - In x86_pmu_read, it doesn't count the undrained values in large PEBS buffers. The issue is introduced with the auto-reload mechanism enabled by commit 851559e35fd5 ("perf/x86/intel: Use the PEBS auto reload mechanism when possible") Also, the userspace RDPMC usage is broken for large PEBS. The issue is introduced with the large PEBS enabled by commit b8241d20699e ("perf/x86/intel: Implement batched PEBS interrupt handling (large PEBS interrupt threshold)") The source code of read_count is as below. struct cpu { int fd; struct perf_event_mmap_page *buf; }; int perf_open(struct cpu *ctx, int cpu) { struct perf_event_attr attr = { .type = PERF_TYPE_HARDWARE, .size = sizeof(struct perf_event_attr), .sample_period = 100000, .config = 0, .sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_TID | PERF_SAMPLE_TIME | PERF_SAMPLE_CPU, .precise_ip = 3, .mmap = 1, .comm = 1, .task = 1, .mmap2 = 1, .sample_id_all = 1, .comm_exec = 1, }; ctx->buf = NULL; ctx->fd = syscall(__NR_perf_event_open, &attr, -1, cpu, -1, 0); if (ctx->fd < 0) { perror("perf_event_open"); return -1; } return 0; } void perf_close(struct cpu *ctx) { close(ctx->fd); if (ctx->buf) munmap(ctx->buf, pagesize); } int main(int ac, char **av) { struct cpu ctx; u64 count; perf_open(&ctx, 0); while (1) { sleep(5); if (read(ctx.fd, &count, 8) != 8) { perror("counter read"); break; } printf("0x%llx\n", count); } perf_close(&ctx); } Kan Liang (4): perf/x86/intel: fix event update for auto-reload perf/x86: introduce read function for x86_pmu perf/x86/intel: drain PEBS buffer in event read perf/x86: fix: disable userspace RDPMC usage for large PEBS arch/x86/events/core.c | 5 ++- arch/x86/events/intel/core.c | 9 +++++ arch/x86/events/intel/ds.c | 79 ++++++++++++++++++++++++++++++++++++++++++-- arch/x86/events/perf_event.h | 3 ++ 4 files changed, 93 insertions(+), 3 deletions(-) -- 2.7.4