Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754612AbaBFTsb (ORCPT ); Thu, 6 Feb 2014 14:48:31 -0500 Received: from honeysuckle.london.02.net ([87.194.255.144]:44877 "EHLO honeysuckle.london.02.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751339AbaBFTs3 (ORCPT ); Thu, 6 Feb 2014 14:48:29 -0500 X-Greylist: delayed 364 seconds by postgrey-1.27 at vger.kernel.org; Thu, 06 Feb 2014 14:48:29 EST From: Mark Davies To: Peter Zijlstra Cc: Vince Weaver , alan@lxorguk.ukuu.org.uk, Ingo Molnar , Stephane Eranian , linux-kernel@vger.kernel.org Subject: Re: [PATCH] perf,x86,p6: Add userspace RDPMC quirk for P6 References: <20140205102718.GF3229@twins.programming.kicks-ass.net> <20140205192012.GL2936@laptop.programming.kicks-ass.net> <20140205194851.GE5126@laptop.programming.kicks-ass.net> Date: Thu, 06 Feb 2014 19:41:37 +0000 In-Reply-To: <20140205194851.GE5126@laptop.programming.kicks-ass.net> (Peter Zijlstra's message of "Wed, 5 Feb 2014 20:48:51 +0100") Message-ID: <871tzgxc3y.fsf@gw.eslaf.co.uk> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter As I reported the problem I thought I better contribute by testing the fix. I took the patch below and managed to change the 3.4.78 code to match and tried to boot my Pentium Pro system but it hung as before. After some investigation I discovered the quirk is not being run, in fact no quirks were being run in init_hw_perf_events as x86_pmu.quirks was NULL. The problem as far as I can see is that the quirk is added to x86_pmu in p6_pmu_init but then x86_pmu is reassigned at the end of that function (x86_pmu = p6_pmu) resetting x86_pmu.quirks to NULL. x86_pmu looks like it is reassigned again in intel_pmu_init to either core_pmu or intel_pmu after the call to p6_pmu_init so I am not sure which x86_pmu.quirks init_hw_perf_events tries to use. Hopefully that makes sense. Mark Davies On Wed, Feb 05 2014, Peter Zijlstra wrote: > On Wed, Feb 05, 2014 at 08:20:12PM +0100, Peter Zijlstra wrote: >> On Wed, Feb 05, 2014 at 02:16:43PM -0500, Vince Weaver wrote: >> > On Wed, 5 Feb 2014, Peter Zijlstra wrote: >> > >> > > P6 class machines can die hard when PCE gets enabled due to CPU >> > > errata. The safe way it so disable it by default and keep it disabled. >> > > >> > > See errata 26: >> > >> > so you take an errata applicable to a subset of Pentium Pro steppings and >> > apply it to the whole p6 line (which includes the whole way up to Pentium >> > III)? >> > >> > Or am I missing something in the documentation you link to? >> >> I forgot it went all the way to P-III, let me try and find the other >> erratas. > > OK, Just checked the P-II errata and its not there anymore, so I suppose > only Family 6 model 1 should have this quirk. > > Updated patch below. > > --- > Subject: perf,x86,p6: Add userspace RDPMC quirk for PPro > From: Peter Zijlstra > Date: Wed Feb 5 11:17:46 CET 2014 > > PPro machines can die hard when PCE gets enabled due to CPU errata. The > safe way it so disable it by default and keep it disabled. > > See errata 26: > > http://download.intel.com/design/archives/processors/pro/docs/24268935.pdf > > Cc: Alan Cox > Reported-by: Mark Davies > Signed-off-by: Peter Zijlstra > Link: http://lkml.kernel.org/n/tip-jnbn0qpt3t7ogk4c2q79yq90@git.kernel.org > --- > arch/x86/kernel/cpu/perf_event.c | 6 +++++- > arch/x86/kernel/cpu/perf_event.h | 1 + > arch/x86/kernel/cpu/perf_event_p6.c | 35 +++++++++++++++++++++++++---------- > 3 files changed, 31 insertions(+), 11 deletions(-) > > --- a/arch/x86/kernel/cpu/perf_event.c > +++ b/arch/x86/kernel/cpu/perf_event.c > @@ -1521,6 +1521,8 @@ static int __init init_hw_perf_events(vo > > pr_cont("%s PMU driver.\n", x86_pmu.name); > > + x86_pmu.attr_rdpmc = 1; /* enable userspace RDPMC usage by default */ > + > for (quirk = x86_pmu.quirks; quirk; quirk = quirk->next) > quirk->func(); > > @@ -1534,7 +1536,6 @@ static int __init init_hw_perf_events(vo > __EVENT_CONSTRAINT(0, (1ULL << x86_pmu.num_counters) - 1, > 0, x86_pmu.num_counters, 0, 0); > > - x86_pmu.attr_rdpmc = 1; /* enable userspace RDPMC usage by default */ > x86_pmu_format_group.attrs = x86_pmu.format_attrs; > > if (x86_pmu.event_attrs) > @@ -1820,6 +1821,9 @@ static ssize_t set_attr_rdpmc(struct dev > if (ret) > return ret; > > + if (x86_pmu.attr_rdpmc_broken) > + return -ENOTSUPP; > + > if (!!val != !!x86_pmu.attr_rdpmc) { > x86_pmu.attr_rdpmc = !!val; > smp_call_function(change_rdpmc, (void *)val, 1); > --- a/arch/x86/kernel/cpu/perf_event.h > +++ b/arch/x86/kernel/cpu/perf_event.h > @@ -409,6 +409,7 @@ struct x86_pmu { > /* > * sysfs attrs > */ > + int attr_rdpmc_broken; > int attr_rdpmc; > struct attribute **format_attrs; > struct attribute **event_attrs; > --- a/arch/x86/kernel/cpu/perf_event_p6.c > +++ b/arch/x86/kernel/cpu/perf_event_p6.c > @@ -231,20 +231,35 @@ static __initconst const struct x86_pmu > > }; > > +static __init void p6_pmu_rdpmc_quirk(void) > +{ > + pr_warn("Userspace RDPMC support disabled due to CPU errata\n"); > + x86_pmu.attr_rdpmc_broken = 1; > + x86_pmu.attr_rdpmc = 0; > +} > + > __init int p6_pmu_init(void) > { > switch (boot_cpu_data.x86_model) { > - case 1: > - case 3: /* Pentium Pro */ > - case 5: > - case 6: /* Pentium II */ > - case 7: > - case 8: > - case 11: /* Pentium III */ > - case 9: > - case 13: > - /* Pentium M */ > + case 1: /* Pentium Pro */ > + x86_add_quirk(p6_pmu_rdpmc_quirk); > break; > + > + case 3: /* Pentium II - Klamath */ > + case 5: /* Pentium II - Deschutes */ > + case 6: /* Pentium II - Mendocino */ > + break; > + > + case 7: /* Pentium III - Katmai */ > + case 8: /* Pentium III - Coppermine */ > + case 10: /* Pentium III Xeon */ > + case 11: /* Pentium III - Tualatin */ > + break; > + > + case 9: /* Pentium M - Banias */ > + case 13: /* Pentium M - Dothan */ > + break; > + > default: > pr_cont("unsupported p6 CPU model %d ", > boot_cpu_data.x86_model); -- 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/