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

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Message-ID: <92f48c1c-3235-49b2-aabd-7da87ad3febc@google.com>
Date:   Wed, 4 Oct 2023 20:18:12 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Jiaqi Yan <jiaqiyan@...gle.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        "Grimm, Jon" <jon.grimm@....com>, dave.hansen@...ux.intel.com,
        vilas.sridharan@....com
cc:     Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        linuxarm@...wei.com, shiju.jose@...wei.com,
        linux-acpi@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, rafael@...nel.org, lenb@...nel.org,
        naoya.horiguchi@....com, james.morse@....com, david@...hat.com,
        jthoughton@...gle.com, somasundaram.a@....com,
        erdemaktas@...gle.com, pgonda@...gle.com, duenwen@...gle.com,
        mike.malvestuto@...el.com, gthelen@...gle.com,
        tanxiaofei@...wei.com, prime.zeng@...ilicon.com
Subject: Re: [RFC PATCH 2/9] memory: scrub: sysfs: Add Documentation entries
 for set of scrub attributes

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?