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

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

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