Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755112AbbFEPm7 (ORCPT ); Fri, 5 Jun 2015 11:42:59 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:46683 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754831AbbFEPm6 (ORCPT ); Fri, 5 Jun 2015 11:42:58 -0400 Date: Fri, 5 Jun 2015 17:42:47 +0200 From: Peter Zijlstra To: Imre Palik Cc: Paul Mackerras , Ingo Molnar , Arnaldo Carvalho de Melo , Thomas Gleixner , "H. Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, "Palik, Imre" , Anthony Liguori Subject: Re: [PATCH v2] perf: honoring the architectural performance monitoring version Message-ID: <20150605154247.GI19282@twins.programming.kicks-ass.net> References: <1433518125-27169-1-git-send-email-imrep.amz@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1433518125-27169-1-git-send-email-imrep.amz@gmail.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2923 Lines: 85 On Fri, Jun 05, 2015 at 05:28:45PM +0200, Imre Palik wrote: > From: "Palik, Imre" > > Architectural performance monitoring version 1 doesn't support fixed > counters. Currently, even if a hypervisor advertises support for > architectural performance monitoring version 1, perf may still tries to use > the fixed counters, as the constraints are set up based on the CPU model. > > This patch ensures that perf honors the architectural performance > monitoring version returned by CPUID, and it only uses the fixed counters > for version two and above. > > Some of the ideas in this patch are coming from Peter Zijlstra. > > Signed-off-by: Imre Palik > Cc: Anthony Liguori > --- > arch/x86/kernel/cpu/perf_event_intel.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c > index 3998131..bde66aa 100644 > --- a/arch/x86/kernel/cpu/perf_event_intel.c > +++ b/arch/x86/kernel/cpu/perf_event_intel.c > @@ -1870,7 +1870,7 @@ x86_get_event_constraints(struct cpu_hw_events *cpuc, int idx, > for_each_event_constraint(c, x86_pmu.event_constraints) { > if ((event->hw.config & c->cmask) == c->code) { > event->hw.flags |= c->flags; > - return c; > + return c->idxmsk64 ? c : NULL; One too many spaces there :-) Returning c as found, even with empty idxmsk is fine. Also, I think this is broken, I think we hard assume x86_get_event_constraints() returns a valid constraint, see for example: x86_schedule_event(): c = x86_pmu.get_event_constraints() = intel_get_event_constraints() = __intel_get_event_constraints() = x86_get_event_constraints(); cpuc->event_constraint[i] = c; ... c = cpuc->event_constraint[i]; if (!test_bit(hwc->idx, c->idxmask)) <-- *boom* > @@ -3341,9 +3341,12 @@ __init int intel_pmu_init(void) > for_each_event_constraint(c, x86_pmu.event_constraints) { > if (c->cmask != FIXED_EVENT_FLAGS > || c->idxmsk64 == INTEL_PMC_MSK_FIXED_REF_CYCLES) { > + c->idxmsk64 &= > + ~(~0UL << (INTEL_PMC_IDX_FIXED + x86_pmu.num_counters_fixed)); If you change idxmsk64 you also need to update weight. > continue; > } > - > + c->idxmsk64 &= > + ~(~0UL << (INTEL_PMC_IDX_FIXED + x86_pmu.num_counters_fixed)); > c->idxmsk64 |= (1ULL << x86_pmu.num_counters) - 1; > c->weight += x86_pmu.num_counters; And since we're now not unconditionally adding num_counters bits, that weight update is broken. For both sites, something like: c->weight = hweight64(c->idxmsk64); Will recompute the weight. Thanks! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/