Re: [PATCH -v4] x86: MCE: Re-implement MCE log ring buffer as per-CPU ring buffer

Huang Ying
2009-06-05T08:39:50Z

On Fri, 2009-06-05 at 16:28 +0800, Hidetoshi Seto wrote:
> Huang Ying wrote:
> > On Fri, 2009-06-05 at 15:01 +0800, Hidetoshi Seto wrote:
> >> Huang Ying wrote:
> >>> struct mce_log {
> >>> - char signature[12]; /* "MACHINECHECK" */
> >>> + char signature[12]; /* "MACHINECHEC2" */
> >>> unsigned len; /* = MCE_LOG_LEN */
> >>> - unsigned next;
> >>> unsigned flags;
> >>> unsigned pad0;
> >>> - struct mce entry[MCE_LOG_LEN];
> >>> + struct mce_log_cpu *mcelog_cpus;
> >>> };
> >> What is this *mcelog_cpus to be used for?
> >> It seems it will point one of per-CPU buffers (maybe cpu#0's buffer)
> >> if I have read the following mce_log_init() correctly.
> >
> > It is mainly used by something like kdump, which can search
> > "MACHINECHEC2", and analyze mce_log. mcelog_cpus can help kdump find the
> > real mcelog storage.
>
> Hum, but it help tools only to find one of buffers, not to find all.
>
> I think it would be better help for tools if we have another signature
> on struct mce_log_cpu, e.g.:
>
> +struct mce_log_cpu {
> + char signature[**]; /* "MCE_LOG_CPU_VER_1" or so */
> + __u32 cpuid; /* cpuid or extcpu, same as struct mce */
> + int head;
> + int tail;
> + unsigned long flags;
> + struct mce entry[MCE_LOG_LEN];
> +};
>
> How about this?

+ mcelog.mcelog_cpus = &per_cpu_var(mce_log_cpus);

So mcelog.mcelog_cpus are pointed to the buffers of all CPUs, not just
that of one CPU. You can find them by analyzing PER cpu data structure.

Best Regards,
Huang Ying