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SubjectRe: [V2 PATCH] perf/x86/intel: Don't enable freeze-on-smi for PerfMon V1
On Wed, Apr 25, 2018 at 02:57:17PM -0400, kan.liang@linux.intel.com wrote:
> From: Kan Liang <kan.liang@linux.intel.com>
>
> The SMM freeze feature was introduced since PerfMon V2. But the current
> code unconditionally enables the feature for all platforms. It can
> generate #GP exception, if the related FREEZE_WHILE_SMM bit is set for
> the machine with PerfMon V1.
>
> To disable the feature for PerfMon V1, perf needs to
> - Remove the freeze_on_smi sysfs entry by moving intel_pmu_attrs to
> intel_pmu, which is only applied to PerfMon V2 and later.
> - Check the PerfMon version before flipping the SMM bit when starting CPU
>
> Fixes: 6089327f5424 ("perf/x86: Add sysfs entry to freeze counters on SMI")
> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

> ---
>
> Change since V1
> - Modified the changelog.
>
> arch/x86/events/intel/core.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
> index 4f2a5c7..08be8ed 100644
> --- a/arch/x86/events/intel/core.c
> +++ b/arch/x86/events/intel/core.c
> @@ -3346,7 +3346,8 @@ static void intel_pmu_cpu_starting(int cpu)
>
> cpuc->lbr_sel = NULL;
>
> - flip_smm_bit(&x86_pmu.attr_freeze_on_smi);
> + if (x86_pmu.version > 1)
> + flip_smm_bit(&x86_pmu.attr_freeze_on_smi);
>
> if (!cpuc->shared_regs)
> return;
> @@ -3509,6 +3510,8 @@ static __initconst const struct x86_pmu core_pmu = {
> .cpu_dying = intel_pmu_cpu_dying,
> };
>
> +static struct attribute *intel_pmu_attrs[];
> +
> static __initconst const struct x86_pmu intel_pmu = {
> .name = "Intel",
> .handle_irq = intel_pmu_handle_irq,
> @@ -3540,6 +3543,8 @@ static __initconst const struct x86_pmu intel_pmu = {
> .format_attrs = intel_arch3_formats_attr,
> .events_sysfs_show = intel_event_sysfs_show,
>
> + .attrs = intel_pmu_attrs,
> +
> .cpu_prepare = intel_pmu_cpu_prepare,
> .cpu_starting = intel_pmu_cpu_starting,
> .cpu_dying = intel_pmu_cpu_dying,
> @@ -3918,8 +3923,6 @@ __init int intel_pmu_init(void)
>
> x86_pmu.max_pebs_events = min_t(unsigned, MAX_PEBS_EVENTS, x86_pmu.num_counters);
>
> -
> - x86_pmu.attrs = intel_pmu_attrs;
> /*
> * Quirk: v2 perfmon does not report fixed-purpose events, so
> * assume at least 3 events, when not running in a hypervisor:
> --
> 2.4.11
>

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