From 1af22eba248efe2de25658041a80a3d40fb3e92e Mon Sep 17 00:00:00 2001 From: Kan Liang Date: Mon, 12 Feb 2018 14:20:35 -0800 Subject: [PATCH] perf/x86/intel: Disable userspace RDPMC usage for large PEBS Userspace RDPMC cannot possibly work for large PEBS, which was introduced in: b8241d20699e ("perf/x86/intel: Implement batched PEBS interrupt handling (large PEBS interrupt threshold)") When the PEBS interrupt threshold is larger than one, there is no way to get exact auto-reload times and value for userspace RDPMC. Disable the userspace RDPMC usage when large PEBS is enabled. The only exception is when the PEBS interrupt threshold is 1, in which case user-space RDPMC works well even with auto-reload events. Signed-off-by: Kan Liang Signed-off-by: Peter Zijlstra (Intel) Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Cc: acme@kernel.org Fixes: b8241d20699e ("perf/x86/intel: Implement batched PEBS interrupt handling (large PEBS interrupt threshold)") Link: http://lkml.kernel.org/r/1518474035-21006-6-git-send-email-kan.liang@linux.intel.com Signed-off-by: Ingo Molnar --- arch/x86/events/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index 00a6251981d2..9c86e10f1196 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -2117,7 +2117,8 @@ static int x86_pmu_event_init(struct perf_event *event) event->destroy(event); } - if (READ_ONCE(x86_pmu.attr_rdpmc)) + if (READ_ONCE(x86_pmu.attr_rdpmc) && + !(event->hw.flags & PERF_X86_EVENT_FREERUNNING)) event->hw.flags |= PERF_X86_EVENT_RDPMC_ALLOWED; return err; -- 2.30.2