From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753586AbdBNTtI (ORCPT ); Tue, 14 Feb 2017 14:49:08 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:52116 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751796AbdBNTtD (ORCPT ); Tue, 14 Feb 2017 14:49:03 -0500 Date: Tue, 14 Feb 2017 20:48:54 +0100 From: Peter Zijlstra To: Alexander Shishkin Cc: Ingo Molnar , linux-kernel@vger.kernel.org, vince@deater.net, eranian@google.com, Arnaldo Carvalho de Melo , Borislav Petkov , Thomas Gleixner Subject: Re: [PATCH 1/2] perf/x86/intel/pt: Fail event scheduling on conflict with VMX Message-ID: <20170214194854.GK6536@twins.programming.kicks-ass.net> References: <20170214132416.26400-1-alexander.shishkin@linux.intel.com> <20170214132416.26400-2-alexander.shishkin@linux.intel.com> <20170214135620.GN6500@twins.programming.kicks-ass.net> <87d1eklpb9.fsf@ashishki-desk.ger.corp.intel.com> <20170214162702.GR6500@twins.programming.kicks-ass.net> <874lzwlmch.fsf@ashishki-desk.ger.corp.intel.com> <20170214183807.GT6500@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170214183807.GT6500@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 14, 2017 at 07:38:07PM +0100, Peter Zijlstra wrote: > Right, so I question the whole 'lets not schedule PT when VMX' premise, > it leads to inconsistencies all over. How about we treat it like > ->add() succeeded and VMX simply results in no output. > > Esp. when you then emit 'fake' data into/from a vmlaunch/vmresume > instruction. That is, what about something like the below? (completely untested for obvious raisins). That should schedule PT like normal, and where VMXON will auto-clear TraceEn for us, we make VMXOFF set it again. --- arch/x86/events/intel/pt.c | 38 ++++++++++++++++++++++++++------------ arch/x86/events/intel/pt.h | 1 + 2 files changed, 27 insertions(+), 12 deletions(-) diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c index 5900471ee508..a42fa1bef761 100644 --- a/arch/x86/events/intel/pt.c +++ b/arch/x86/events/intel/pt.c @@ -411,6 +411,7 @@ static u64 pt_config_filters(struct perf_event *event) static void pt_config(struct perf_event *event) { + struct pt *pt = this_cpu_ptr(&pt_ctx); u64 reg; if (!event->hw.itrace_started) { @@ -429,11 +430,14 @@ static void pt_config(struct perf_event *event) reg |= (event->attr.config & PT_CONFIG_MASK); event->hw.config = reg; - wrmsrl(MSR_IA32_RTIT_CTL, reg); + + if (!pt->vmx_on) + wrmsrl(MSR_IA32_RTIT_CTL, reg); } static void pt_config_stop(struct perf_event *event) { + struct pt *pt = this_cpu_ptr(&pt_ctx); u64 ctl = READ_ONCE(event->hw.config); /* may be already stopped by a PMI */ @@ -441,7 +445,9 @@ static void pt_config_stop(struct perf_event *event) return; ctl &= ~RTIT_CTL_TRACEEN; - wrmsrl(MSR_IA32_RTIT_CTL, ctl); + + if (!pt->vmx_on) + wrmsrl(MSR_IA32_RTIT_CTL, ctl); WRITE_ONCE(event->hw.config, ctl); @@ -1174,10 +1180,12 @@ void intel_pt_interrupt(void) /* * If VMX is on and PT does not support it, don't touch anything. */ - if (READ_ONCE(pt->vmx_on)) + if (READ_ONCE(pt->vmx_on)) { + WRITE_ONCE(pt->vmx_pmi_pending, 1); return; + } - if (!event) + if (WARN_ON(!event)) /* should be set if handle_nmi */ return; pt_config_stop(event); @@ -1236,13 +1244,22 @@ void intel_pt_handle_vmx(int on) */ local_irq_save(flags); WRITE_ONCE(pt->vmx_on, on); + if (on) + goto done; - if (on) { - /* prevent pt_config_stop() from writing RTIT_CTL */ - event = pt->handle.event; - if (event) - event->hw.config = 0; + /* OTOH, if we just did VMXOFF, we need to set TraceEn again */ + event = pt->handle.event; + if (!event) + goto done; + + if (pt->vmx_pmi_pending) { + intel_pt_interrupt(); + pt->vmx_pmi_pending = 0; + } else { + wrmsrl(MSR_IA32_RTIT_CTL, event->hw.config); } + +done: local_irq_restore(flags); } EXPORT_SYMBOL_GPL(intel_pt_handle_vmx); @@ -1257,9 +1274,6 @@ static void pt_event_start(struct perf_event *event, int mode) struct pt *pt = this_cpu_ptr(&pt_ctx); struct pt_buffer *buf; - if (READ_ONCE(pt->vmx_on)) - return; - buf = perf_aux_output_begin(&pt->handle, event); if (!buf) goto fail_stop; diff --git a/arch/x86/events/intel/pt.h b/arch/x86/events/intel/pt.h index 53473c21b554..98ed385e187b 100644 --- a/arch/x86/events/intel/pt.h +++ b/arch/x86/events/intel/pt.h @@ -187,6 +187,7 @@ struct pt { struct pt_filters filters; int handle_nmi; int vmx_on; + int vmx_pmi_pending; }; #endif /* __INTEL_PT_H__ */