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

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Message-ID: <1496946370.9288.7.camel@hpe.com>
Date:   Thu, 8 Jun 2017 18:26:36 +0000
From:   "Kani, Toshimitsu" <toshi.kani@....com>
To:     "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "Knippers, Linda" <linda.knippers@....com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "vishal.l.verma@...el.com" <vishal.l.verma@...el.com>
Subject: Re: [PATCH] Add support of NVDIMM memory error notification in ACPI
 6.2

On Thu, 2017-06-08 at 11:37 -0600, Toshi Kani wrote:
> On Thu, 2017-06-08 at 10:34 -0700, Dan Williams wrote:
> > On Thu, Jun 8, 2017 at 10:30 AM, Linda Knippers <linda.knippers@hpe
> > .c
> > om> wrote:
> > [..]
> > > Wasn't Dan concerned about how the OS can know whether the FW
> > > supports that bit in the Start ARS?
> > > 
> > > The Query ARS Capabilities DSM has a bit that tells the OS
> > > whether the platform supports the notification and the point of
> > > the notification was to tell the OS it could do a Start ARS with
> > > bit 1 set.  Of course, if you get the notification then that
> > > means the platform has the capability to deliver it, but it might
> > > not hurt to check the flag from the Query Capabilities bit.
> > 
> > Good point, yes, I think it is safe to assume that a BIOS that
> > claims to support un-correctable error notification also supports
> > this Start ARS flag.
> 
> Yes, ACPI 6.2, section 9.20.7.2, defines that:
> 
>       Upon receiving the notification, the OSPM may decide to issue
>       a Start ARS with Flags Bit [1] set to prepare for the retrieval
>       of existing records and issue the Query ARS Status function to
>       retrieve the records.
> 
> So, I believe it is safe to assume that BIOS supporting 0x81 also
> supports flags Bit [1].  Sorry, this is what I should have said in my
> previous email...

To reiterate my thinking, I believe the statement above clarifies that
the OS can assume BIOS support of Flags Bit[1] upon receiving a 0x81
notification.  Since BIOS may also support Flags Bit[1] without
supporting this 0x81 (in which case I do not know how to detect it, but
BIOS should simply ignore this bit when not supporting it), I am not
going to add a check/restriction that 0x81 support is necessary to set
Bit[1] in the scan function.

Thanks,
-Toshi