linux-kernel - Re: [RFC PATCH 4/5] acpi/hmat: Register special purpose memory as a device

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Date:   Tue, 9 Apr 2019 05:13:18 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-kernel@...r.kernel.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Keith Busch <keith.busch@...el.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        vishal.l.verma@...el.com, x86@...nel.org, linux-mm@...ck.org,
        linux-nvdimm@...ts.01.org
Subject: Re: [RFC PATCH 4/5] acpi/hmat: Register special purpose memory as a
 device

On Thu, Apr 04, 2019 at 12:08:49PM -0700, Dan Williams wrote:
> Memory that has been tagged EFI_SPECIAL_PURPOSE, and has performance
> properties described by the ACPI HMAT is expected to have an application
> specific consumer.
> 
> Those consumers may want 100% of the memory capacity to be reserved from
> any usage by the kernel. By default, with this enabling, a platform
> device is created to represent this differentiated resource.

This sounds more than weird.  Since when did we let the firmware decide
who can use the memory?