linux-kernel - RE: [PATCH 1/2] x86/mce: Disable preemption for CPER decoding

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Date:   Thu, 22 Jun 2023 19:42:49 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Yazen Ghannam <yazen.ghannam@....com>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>
Subject: RE: [PATCH 1/2] x86/mce: Disable preemption for CPER decoding

> 2) Split mce_setup() into global and per_cpu parts. The memset(), cpuid, 
> etc. would be global, and the cpu_data()* and rdmsr() would be per_cpu.

That sounds good. So global is:

        memset(m, 0, sizeof(struct mce));
        /* need the internal __ version to avoid deadlocks */
        m->time = __ktime_get_real_seconds();
        m->cpuvendor = boot_cpu_data.x86_vendor;
        m->mcgcap = __rdmsr(MSR_IA32_MCG_CAP);
        m->microcode = boot_cpu_data.microcode;
        m->cpuid = cpuid_eax(1);

Though that last one is perhaps per-cpu if you want to allow for mixed-stepping systems.
Perhaps m->time also? Questionable whether it is useful to log time this record
was created, when it refers to something much earlier in the BERT case.

and per-cpu is:

        m->cpu = m->extcpu = smp_processor_id();
        m->socketid = cpu_data(m->extcpu).phys_proc_id;
        m->apicid = cpu_data(m->extcpu).initial_apicid;
        m->ppin = cpu_data(m->extcpu).ppin;

> Option #2 can also be used in apei_mce_report_mem_error(), I think.

Agreed.

-Tony