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SubjectRe: [PATCH 3/4] x86, mce: Add persistent MCE event

* Borislav Petkov <bp@amd64.org> wrote:

> +static struct perf_event_attr pattr = {
> + .type = PERF_TYPE_TRACEPOINT,
> + .size = sizeof(pattr),
> + .sample_type = PERF_SAMPLE_RAW,
> + .persistent = 1,
> +};
> +
> +static struct dentry *mce_add_event_debugfs(struct perf_event *event, int cpu)
> +{
> + char buf[14];
> +
> + sprintf(buf, "mce_record%d", cpu);
> +
> + return debugfs_create_file(buf, S_IRUGO | S_IWUSR,
> + mce_get_debugfs_dir(),
> + event, &perf_pers_fops);
> +}
> +
> +#define MCE_BUF_PAGES 4
> +
> +static int mce_enable_perf_event_on_cpu(int cpu)
> +{
> + struct mce_tp_desc *d = &per_cpu(mce_event, cpu);
> + int err = -EINVAL;
> +
> + d->event = perf_enable_persistent_event(&pattr, cpu, MCE_BUF_PAGES);
> + if (IS_ERR(d->event)) {
> + printk(KERN_ERR "MCE: Error enabling event on cpu %d\n", cpu);
> + goto ret;
> + }
> +
> + d->debugfs_entry = mce_add_event_debugfs(d->event, cpu);
> + if (!d->debugfs_entry) {
> + printk(KERN_ERR "MCE: Error adding event debugfs entry on cpu %d\n", cpu);
> + goto disable;
> + }
> +
> + return 0;
> +
> +disable:
> + perf_disable_persistent_event(d->event, cpu);
> +
> +ret:
> + return err;
> +}
> +
> +static void mce_disable_perf_event_on_cpu(int cpu)
> +{
> + struct mce_tp_desc *d = &per_cpu(mce_event, cpu);
> + debugfs_remove(d->debugfs_entry);
> + perf_disable_persistent_event(d->event, cpu);
> +}
> +
> +static __init int mcheck_init_persistent_event(void)
> +{
> + int cpu, err = 0;
> +
> + get_online_cpus();
> +
> + pattr.config = event_mce_record.event.type;
> + pattr.sample_period = 1;
> + pattr.wakeup_events = 1;
> +
> + for_each_online_cpu(cpu)
> + if (mce_enable_perf_event_on_cpu(cpu))
> + goto err_unwind;
> +
> + goto unlock;
> +
> +err_unwind:
> + err = -EINVAL;
> + for (--cpu; cpu >= 0; cpu--)
> + mce_disable_perf_event_on_cpu(cpu);
> +
> +unlock:
> + put_online_cpus();
> +
> + return err;
> +}
> +
> +/*
> + * This has to run after event_trace_init()
> + */
> +device_initcall(mcheck_init_persistent_event);

Looks quite generic - shouldnt this bit be generalized a bit more into
kernel/events/? When other places (and other platforms) want to add a
persistent event they would thus have your new facility available as well.

Except this bit:

> /* Get notified when a cpu comes on/off. Be hotplug friendly. */
> static int __cpuinit
> mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
> @@ -2068,6 +2154,7 @@ mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
> mce_create_device(cpu);
> if (threshold_cpu_callback)
> threshold_cpu_callback(action, cpu);
> + mce_enable_perf_event_on_cpu(cpu);
> break;
> case CPU_DEAD:
> case CPU_DEAD_FROZEN:
> @@ -2077,6 +2164,7 @@ mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
> break;
> case CPU_DOWN_PREPARE:
> case CPU_DOWN_PREPARE_FROZEN:
> + mce_disable_perf_event_on_cpu(cpu);
> del_timer_sync(t);
> smp_call_function_single(cpu, mce_disable_cpu, &action, 1);
> break;
> @@ -2088,6 +2176,7 @@ mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
> add_timer_on(t, cpu);
> }
> smp_call_function_single(cpu, mce_reenable_cpu, &action, 1);
> + mce_enable_perf_event_on_cpu(cpu);
> break;
> case CPU_POST_DEAD:
> /* intentionally ignoring frozen here */

which looks a bit x86 specific.

Thanks,

Ingo


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