linux-kernel - Re: [PATCH v7] x86/mce: retrieve poison range from hardware

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Message-ID: <b3880db6-6731-1d1b-144f-1080a033ad01@oracle.com>
Date:   Thu, 25 Aug 2022 16:29:47 +0000
From:   Jane Chu <jane.chu@...cle.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     "tony.luck@...el.com" <tony.luck@...el.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "hch@....de" <hch@....de>,
        "nvdimm@...ts.linux.dev" <nvdimm@...ts.linux.dev>
Subject: Re: [PATCH v7] x86/mce: retrieve poison range from hardware

On 8/23/2022 9:51 AM, Borislav Petkov wrote:
> On Tue, Aug 02, 2022 at 01:50:53PM -0600, Jane Chu 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.
> 
> What I'm missing from this text here is, what *is* the mce->misc LSB
> field in human speak? What does that field denote?
> 
> What effect does that field have on error injection
Tony has replied.

> 
> And so on.
> 
>> 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.
> 
> Rely on hardware? You're changing this to rely on what the firmware
> reports.
> 
> That mem_err thing comes from a BIOS table AFAICT.
> 

Would fix the comment to indicate "relying on firmware" help?
Is there other concern?

thanks!
-jane

> ...
> 
> Thx.
>