linux-kernel - Re: [PATCH] Add support of NVDIMM memory error notification in ACPI 6.2

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Message-ID: <CAPcyv4hwhRc6+JW8m3zVn_tKz__wE9BHOfpjy69RS6OwiqV-PA@mail.gmail.com>
Date:   Wed, 7 Jun 2017 14:06:31 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     "Kani, Toshimitsu" <toshi.kani@....com>
Cc:     "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "Verma, Vishal L" <vishal.l.verma@...el.com>
Subject: Re: [PATCH] Add support of NVDIMM memory error notification in ACPI 6.2

On Wed, Jun 7, 2017 at 1:57 PM, Kani, Toshimitsu <toshi.kani@....com> wrote:
> On Wed, 2017-06-07 at 12:09 -0700, Dan Williams wrote:
>> On Wed, Jun 7, 2017 at 11:49 AM, Toshi Kani <toshi.kani@....com>
>> wrote:
>  :
>> > +
>> > +static void acpi_nfit_uc_error_notify(struct device *dev,
>> > acpi_handle handle)
>> > +{
>> > +       struct acpi_nfit_desc *acpi_desc = dev_get_drvdata(dev);
>> > +
>> > +       acpi_nfit_ars_rescan(acpi_desc);
>>
>> I wonder if we should gate re-scanning with a similar:
>>
>>     if (acpi_desc->scrub_mode == HW_ERROR_SCRUB_ON)
>>
>> ...check that we do in the mce notification case? Maybe not since we
>> don't get an indication of where the error is without a rescan.
>
> I think this mce case is different since the MCE handler already knows
> where the new poison location is and can update badblocks information
> for it.  Starting ARS is an optional precaution.
>
>> However, at a minimum I think we need support for the new Start ARS
>> flag ("If set to 1 the firmware shall return data from a previous
>> scrub, if any, without starting a new scrub") and use that for this
>> case.
>
> That's an interesting idea.  But I wonder how users know if it is OK to
> set this flag as it relies on BIOS implementation that is not described
> in ACPI...

Ugh, you're right. We might need a revision-id=2 version of Start ARS
so software knows that the BIOS is aware of the new flag.