linux-kernel - Re: [HMM v13 07/18] mm/ZONE_DEVICE/x86: add support for un-addressable device memory

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Message-ID: <33e9c941-ac57-3dfd-2ed9-c1d058a57d8f@gmail.com>
Date:   Mon, 21 Nov 2016 13:08:56 +1100
From:   Balbir Singh <bsingharora@...il.com>
To:     Jérôme Glisse <jglisse@...hat.com>,
        akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Cc:     John Hubbard <jhubbard@...dia.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [HMM v13 07/18] mm/ZONE_DEVICE/x86: add support for
 un-addressable device memory



On 19/11/16 05:18, Jérôme Glisse wrote:
> It does not need much, just skip populating kernel linear mapping
> for range of un-addressable device memory (it is pick so that there
> is no physical memory resource overlapping it). All the logic is in
> share mm code.
> 
> Only support x86-64 as this feature doesn't make much sense with
> constrained virtual address space of 32bits architecture.
> 

Is there a reason this would not work on powerpc64 for example?
Could you document the limitations -- testing/APIs/missing features?

Balbir Singh.