Re: [PATCH 2/2] acpi, apei: use appropriate pgprot_t to map GHES memory

[Zhang, Jonathan Zhixiong]

On 8/25/2015 1:59 AM, Ingo Molnar wrote:
> * Zhang, Jonathan Zhixiong <zjzhang@xxxxxxxxxxxxxx> wrote:
>
> > On 8/22/2015 2:24 AM, Ingo Molnar wrote:
> > > * Jonathan (Zhixiong) Zhang <zjzhang@xxxxxxxxxxxxxx> wrote:
> > >
> > > > From: "Jonathan (Zhixiong) Zhang" <zjzhang@xxxxxxxxxxxxxx>
> > > >
> > > > With ACPI APEI firmware first handling, generic hardware error
> > > > record is updated by firmware in GHES memory region. On an arm64
> > > > platform, firmware updates GHES memory region with uncached
> > > > access attribute, and then Linux reads stale data from cache.
> > >
> > > This paragraph *still* doesn't parse for me. It's not any English
> > > I can recognize: what is a 'With ACPI APEI firmware first handling'?
> > APEI is ACPI Platform Error Interface; it is part of ACPI spec,
> > defining the aspect of hardware error handling. "firmware first
> > handling" is a terminology used in APEI. It describes such mechanism
> > that when hardware error happens, firmware intersects/handles such
> > hardware error, formulates hardware error record and writes the record
> > to GHES memory region, notifies the kernel through NMI/interrupt, then
> > the kernel GHES driver grabs the error record from the GHES memory
> > region.
>
> Argh. So how about translating that to English and putting that misnomer into
> scare quotes, and saying something like:
>
>    If the ACPI APEI firmware handles the error first (called "firmware first
>    handling"), the generic hardware error record is updated by the firmware in the
>    GHES memory region.
>
> ( Also note all the missing articles I added for readability. The rest of the
>    changelog is missing articles as well. )
Thank you very much, Ingo. Input are taken.
> > > ... plus what this changelog still doesn't mention is the most important part
> > > of any bug fix description: how does the user notice this in practice and why
> > > does he care?
> >
> > The changelog mentioned that Linux would read stale data from cache. When stale
> > data is read, kernel reports there is no new hardware error when there actually
> > is.
>
> Note that this is the most valuable sentence so far, in this whole changelog and
> discussion. And we needed how many emails to get to this point?
>
> obviously saying 'stale data' in itself does not mean much - it could mean a
> harmless inconsistency nobody really cares about, or in fact it could mean
> something more serious:
Sure, makes sense.
> > [...] This may lead to further damage in various scenarios, such as error
> > propagation caused data corruption.
>
> Please outline this better. How users are affected in practice is far more
> important than any other detail.
Yes, will do. I just sent out an update for your review.
> Thanks,
>
> 	Ingo

--
Jonathan (Zhixiong) Zhang
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
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