Subject: Re: [HMM v13 05/18] mm/ZONE_DEVICE/devmem_pages_remove: allow early
 removal of device memory
To: Jerome Glisse <jglisse@redhat.com>
References: <1479493107-982-1-git-send-email-jglisse@redhat.com>
 <1479493107-982-6-git-send-email-jglisse@redhat.com>
 <5832CE7A.3060802@linux.vnet.ibm.com> <20161121123910.GE2392@redhat.com>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, John Hubbard <jhubbard@nvidia.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Ross Zwisler <ross.zwisler@linux.intel.com>
From: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Date: Tue, 22 Nov 2016 10:24:54 +0530
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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, J?r?me 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.