From: Kan Liang Date: Mon, 12 Feb 2018 22:20:35 +0000 (-0800) Subject: perf/x86/intel: Disable userspace RDPMC usage for large PEBS X-Git-Tag: v4.17-rc1~179^2~32 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=1af22eba248efe2de25658041a80a3d40fb3e92e;p=thirdparty%2Fkernel%2Flinux.git 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 --- diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index 00a6251981d20..9c86e10f11966 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;