linux-kernel - Re: [PATCH v3 00/10] EFI Specific Purpose Memory Support

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Date:   Fri, 7 Jun 2019 12:57:49 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Dan Williams <dan.j.williams@...el.com>,
        linux-kernel@...r.kernel.org
Cc:     Dave Jiang <dave.jiang@...el.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Keith Busch <keith.busch@...el.com>,
        kbuild test robot <lkp@...el.com>,
        Andy Shevchenko <andy@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        Vishal Verma <vishal.l.verma@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Len Brown <lenb@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Andy Lutomirski <luto@...nel.org>,
        Darren Hart <dvhart@...radead.org>, linux-nvdimm@...ts.01.org,
        linux-efi@...r.kernel.org
Subject: Re: [PATCH v3 00/10] EFI Specific Purpose Memory Support

On 6/7/19 12:27 PM, Dan Williams wrote:
> In support of optionally allowing either application-exclusive and
> core-kernel-mm managed access to differentiated memory, claim
> EFI_MEMORY_SP ranges for exposure as device-dax instances by default.
> Such instances can be directly owned / mapped by a
> platform-topology-aware application. Alternatively, with the new kmem
> facility [4], the administrator has the option to instead designate that
> those memory ranges be hot-added to the core-kernel-mm as a unique
> memory numa-node. In short, allow for the decision about what software
> agent manages specific-purpose memory to be made at runtime.

It's probably worth noting that the reason the memory lands into the
state of being controlled by device-dax by default is that device-dax is
nice.  It's actually willing and able to give up ownership of the memory
when we ask.  If we added to the core-mm, we'd almost certainly not be
able to get it back reliably.

Anyway, thanks for doing these, and I really hope that the world's
BIOSes actually use this flag.  For the series:

Reviewed-by: Dave Hansen <dave.hansen@...ux.intel.com>