linux-kernel - Re: [PATCH v2 1/2] cper, apei, mce: Pass x86 CPER through the MCA handling chain

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Date:   Tue, 1 Sep 2020 14:36:24 -0500
From:   Yazen Ghannam <yazen.ghannam@....com>
To:     Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-edac@...r.kernel.org,
        linux-efi@...r.kernel.org, linux-acpi@...r.kernel.org,
        devel@...ica.org, Borislav Petkov <bp@...en8.de>,
        Tony Luck <tony.luck@...el.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>,
        Ard Biesheuvel <ardb@...nel.org>
Subject: Re: [PATCH v2 1/2] cper, apei, mce: Pass x86 CPER through the MCA
 handling chain

On Fri, Aug 28, 2020 at 03:33:31PM -0500, Smita Koralahalli wrote:
...
> +int apei_mce_report_x86_error(struct cper_ia_proc_ctx *ctx_info, u64 lapic_id)
> +{
> +	const u64 *i_mce = ((const void *) (ctx_info + 1));
> +	unsigned int cpu;
> +	struct mce m;
> +
> +	if (!boot_cpu_has(X86_FEATURE_SMCA))
> +		return -EINVAL;
> +

This function is called on any context type, but it can only decode
"MSR" types that follow the MCAX register layout used on Scalable MCA
systems.

So I think there should be a couple of checks added:
1) Context type is "MSR".
2) Register layout follows what is expected below. There's no explict
way to do this, since the data is implemenation-specific. But at least
there can be a check that the starting MSR address matches the first
expected register: Bank's MCA_STATUS in MCAX space (0xC0002XX1).

For example:

	(ctx_info->msr_addr & 0xC0002001) == 0xC0002001

The raw value in the example should be defined with a name.

> +	mce_setup(&m);
> +
> +	m.extcpu = -1;
> +	m.socketid = -1;
> +
> +	for_each_possible_cpu(cpu) {
> +		if (cpu_data(cpu).initial_apicid == lapic_id) {
> +			m.extcpu = cpu;
> +			m.socketid = cpu_data(m.extcpu).phys_proc_id;
> +			break;
> +		}
> +	}
> +
> +	m.apicid = lapic_id;
> +	m.bank = (ctx_info->msr_addr >> 4) & 0xFF;
> +	m.status = *i_mce;
> +	m.addr = *(i_mce + 1);
> +	m.misc = *(i_mce + 2);
> +	/* Skipping MCA_CONFIG */
> +	m.ipid = *(i_mce + 4);
> +	m.synd = *(i_mce + 5);
> +
> +	mce_log(&m);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(apei_mce_report_x86_error);
> +

Thanks,
Yazen