linux-kernel - Re: [HMM v13 05/18] mm/ZONE_DEVICE/devmem_pages_remove: allow early removal of device memory

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Message-Id: <5833CF9E.1030804@linux.vnet.ibm.com>
Date:   Tue, 22 Nov 2016 10:24:54 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     Jerome Glisse <jglisse@...hat.com>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, John Hubbard <jhubbard@...dia.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: Re: [HMM v13 05/18] mm/ZONE_DEVICE/devmem_pages_remove: allow early
 removal of device memory

On 11/21/2016 06:09 PM, Jerome Glisse wrote:
> On Mon, Nov 21, 2016 at 04:07:46PM +0530, Anshuman Khandual wrote:
>> On 11/18/2016 11:48 PM, Jérôme Glisse wrote:
>>> HMM wants to remove device memory early before device tear down so add an
>>> helper to do that.
>>
>> Could you please explain why HMM wants to remove device memory before
>> device tear down ?
>>
> 
> Some device driver want to manage memory for several physical devices from a
> single fake device driver. Because it fits their driver architecture better
> and those physical devices can have dedicated link between them.
> 
> Issue is that the fake device driver can outlive any of the real device for a
> long time so we want to be able to remove device memory before the fake device
> goes away to free up resources early.

Got it.