On Thu, Feb 06, 2014 at 07:41:37PM +0000, Mark Davies wrote: > 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.
Right so far. > 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. Note how intel_pmu_init() does: return p6_pmu_init(), so it will never get to the x86_pmu assignment for the ARCH_PERFMON drivers. Yep, thanks for testing and you're (mostly) quite right. We can do the copy early though, if we return -ENODEV nothing will end up using the x86_pmu anyway, so it doesn't matter what lives in there. --- Subject: perf,x86,p6: Add userspace RDPMC quirk for PPro From: Peter Zijlstra <[email protected]> Date: Wed, 5 Feb 2014 20:48:51 +0100 PPro machines can die hard when PCE gets enabled due to a CPU erratum. The safe way it so disable it by default and keep it disabled. See erratum 26 in: http://download.intel.com/design/archives/processors/pro/docs/24268935.pdf Cc: Alan Cox <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Stephane Eranian <[email protected]> Cc: Vince Weaver <[email protected]> Reported-by: Mark Davies <[email protected]> Signed-off-by: Peter Zijlstra <[email protected]> --- arch/x86/kernel/cpu/perf_event.c | 6 +++- arch/x86/kernel/cpu/perf_event.h | 1 arch/x86/kernel/cpu/perf_event_p6.c | 48 ++++++++++++++++++++++++------------ 3 files changed, 39 insertions(+), 16 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 @@ -231,31 +231,49 @@ static __initconst const struct x86_pmu }; +static __init void p6_pmu_rdpmc_quirk(void) +{ + if (boot_cpu_data.x86_mask < 9) { + /* + * PPro erratum 26; fixed in stepping 9 and above. + */ + pr_warn("Userspace RDPMC support disabled due to a CPU erratum\n"); + x86_pmu.attr_rdpmc_broken = 1; + x86_pmu.attr_rdpmc = 0; + } +} + __init int p6_pmu_init(void) { + x86_pmu = p6_pmu; + 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); + pr_cont("unsupported p6 CPU model %d ", boot_cpu_data.x86_model); return -ENODEV; } - x86_pmu = p6_pmu; - memcpy(hw_cache_event_ids, p6_hw_cache_event_ids, sizeof(hw_cache_event_ids)); - return 0; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
