RE: [RFC PATCH 2/9] memory: scrub: sysfs: Add Documentation entries for set of scrub attributes

[Sridharan, Vilas]

[AMD Official Use Only - General]

I do not believe AMD has implemented RASF/RAS2 at all.

We are looking at it, but our initial impression is that it is insufficiently flexible for general use. (Not just for this feature, but for others in the future.)

    -Vilas

-----Original Message-----
From: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Sent: Friday, October 6, 2023 9:02 AM
To: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Jiaqi Yan <jiaqiyan@xxxxxxxxxx>; Luck, Tony <tony.luck@xxxxxxxxx>; Grimm, Jon <Jon.Grimm@xxxxxxx>; dave.hansen@xxxxxxxxxxxxxxx; Sridharan, Vilas <Vilas.Sridharan@xxxxxxx>; linuxarm@xxxxxxxxxx; shiju.jose@xxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; rafael@xxxxxxxxxx; lenb@xxxxxxxxxx; naoya.horiguchi@xxxxxxx; james.morse@xxxxxxx; david@xxxxxxxxxx; jthoughton@xxxxxxxxxx; somasundaram.a@xxxxxxx; erdemaktas@xxxxxxxxxx; pgonda@xxxxxxxxxx; duenwen@xxxxxxxxxx; mike.malvestuto@xxxxxxxxx; gthelen@xxxxxxxxxx; tanxiaofei@xxxxxxxxxx; prime.zeng@xxxxxxxxxxxxx
Subject: Re: [RFC PATCH 2/9] memory: scrub: sysfs: Add Documentation entries for set of scrub attributes

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On Wed, 4 Oct 2023 20:18:12 -0700 (PDT)
David Rientjes <rientjes@xxxxxxxxxx> wrote:

> On Wed, 27 Sep 2023, Jiaqi Yan wrote:
>
> > > > 1. I am not aware of any chip/platform hardware that implemented
> > > > the hw ps part defined in ACPI RASF/RAS2 spec. So I am curious
> > > > what the RAS experts from different hardware vendors think about
> > > > this. For example, Tony and Dave from Intel, Jon and Vilas from
> > > > AMD. Is there any hardware platform (if allowed to disclose)
> > > > that implemented ACPI RASF/RAS2? If so, will vendors continue to
> > > > support the control of patrol scrubber using the ACPI spec? If
> > > > not (as Tony said in [1], will the vendor consider starting some future platform?
> > > >
> > > > If we are unlikely to get the vendor support, creating this ACPI
> > > > specific sysfs API (and the driver implementations) in Linux
> > > > seems to have limited meaning.
> > >
> > > There is a bit of a chicken and egg problem here. Until there is
> > > reasonable support in kernel (or it looks like there will be),
> > > BIOS teams push back on a requirement to add the tables.
> > > I'd encourage no one to bother with RASF - RAS2 is much less
> > > ambiguous.
> >
> > Here mainly to re-ping folks from Intel (Tony and Dave)  and AMD
> > (Jon and Vilas) for your opinion on RAS2.
> >
>
> We'll need to know from vendors, ideally at minimum from both Intel
> and AMD, whether RAS2 is the long-term vision here.  Nothing is set in
> stone, of course, but deciding whether RAS2 is the standard that we
> should be rallying around will help to guide future development
> including in the kernel.
>
> If RAS2 is insufficient for future use cases or we would need to
> support multiple implementations in the kernel for configuring the
> patrol scrubber depending on vendor, that's great feedback to have.
>
> I'd much rather focus on implementing something in the kernel that we
> have some clarity about the vendors supporting, especially when it
> comes with user visible interfaces, as opposed to something that may
> not be used long term.  I think that's a fair ask and that vendor
> feedback is required here?

Agreed and happy to have feedback from Intel and AMD + all the other CPU vendors who make use of ACPI + all the OEMs who add stuff well beyond what Intel and AMD tell them to :)  I'll just note a lot of the ACPI support in the kernel covers stuff not used on mainstream x86 platforms because they are doing something custom and we didn't want 2 + X custom implementations...

Some other interfaces for scrub control (beyond existing embedded ones) will surface in the next few months where RAS2 is not appropriate.

Jonathan