linux-kernel - Re: [PATCH v6] x86/mce: retrieve poison range from hardware

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Message-ID: <YukDlb9SsZ2UlX8o@gmail.com>
Date:   Tue, 2 Aug 2022 12:59:33 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Jane Chu <jane.chu@...cle.com>
Cc:     tony.luck@...el.com, bp@...en8.de, tglx@...utronix.de,
        mingo@...hat.com, dave.hansen@...ux.intel.com, x86@...nel.org,
        linux-edac@...r.kernel.org, dan.j.williams@...el.com,
        linux-kernel@...r.kernel.org, hch@....de, nvdimm@...ts.linux.dev
Subject: Re: [PATCH v6] x86/mce: retrieve poison range from hardware


* Jane Chu <jane.chu@...cle.com> wrote:

> With Commit 7917f9cdb503 ("acpi/nfit: rely on mce->misc to determine
> poison granularity") that changed nfit_handle_mce() callback to report
> badrange according to 1ULL << MCI_MISC_ADDR_LSB(mce->misc), it's been
> discovered that the mce->misc LSB field is 0x1000 bytes, hence injecting
> 2 back-to-back poisons and the driver ends up logging 8 badblocks,
> because 0x1000 bytes is 8 512-byte.
> 
> Dan Williams noticed that apei_mce_report_mem_error() hardcode
> the LSB field to PAGE_SHIFT instead of consulting the input
> struct cper_sec_mem_err record.  So change to rely on hardware whenever
> support is available.
> 
> Link: https://lore.kernel.org/r/7ed50fd8-521e-cade-77b1-738b8bfb8502@oracle.com
> 
> Reviewed-by: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Jane Chu <jane.chu@...cle.com>
> ---
>  arch/x86/kernel/cpu/mce/apei.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/mce/apei.c b/arch/x86/kernel/cpu/mce/apei.c
> index 717192915f28..e2439c7872ba 100644
> --- a/arch/x86/kernel/cpu/mce/apei.c
> +++ b/arch/x86/kernel/cpu/mce/apei.c
> @@ -29,15 +29,27 @@
>  void apei_mce_report_mem_error(int severity, struct cper_sec_mem_err *mem_err)
>  {
>  	struct mce m;
> +	int lsb;
>  
>  	if (!(mem_err->validation_bits & CPER_MEM_VALID_PA))
>  		return;
>  
> +	/*
> +	 * Even if the ->validation_bits are set for address mask,
> +	 * to be extra safe, check and reject an error radius '0',
> +	 * and fallback to the default page size.
> +	 */

speling nit:

  s/fallback/fall back

> +	if (mem_err->validation_bits & CPER_MEM_VALID_PA_MASK)
> +		lsb = find_first_bit((const unsigned long *)
> +			&mem_err->physical_addr_mask, PAGE_SHIFT);

I think we can write this in a shorter form and in a single line:

		lsb = find_first_bit((void *)&mem_err->physical_addr_mask, PAGE_SHIFT);

(Ignore checkpatch if it wants to break the line.)

Untested.

Assuming my suggestion is correct and with those addressed:

  Reviewed-by: Ingo Molnar <mingo@...nel.org>

Thanks,

	Ingo