linux-kernel - Re: [PATCH v3 0/5] mm/hmm/nouveau: add PMD system memory mapping

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Date:   Fri, 10 Jul 2020 13:13:46 -0700
From:   Ralph Campbell <rcampbell@...dia.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     <linux-rdma@...r.kernel.org>, <linux-mm@...ck.org>,
        <nouveau@...ts.freedesktop.org>, <linux-kselftest@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Jerome Glisse <jglisse@...hat.com>,
        "John Hubbard" <jhubbard@...dia.com>,
        Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>, Ben Skeggs <bskeggs@...hat.com>
Subject: Re: [PATCH v3 0/5] mm/hmm/nouveau: add PMD system memory mapping


On 7/10/20 12:27 PM, Jason Gunthorpe wrote:
> On Wed, Jul 01, 2020 at 03:53:47PM -0700, Ralph Campbell wrote:
>> The goal for this series is to introduce the hmm_pfn_to_map_order()
>> function. This allows a device driver to know that a given 4K PFN is
>> actually mapped by the CPU using a larger sized CPU page table entry and
>> therefore the device driver can safely map system memory using larger
>> device MMU PTEs.
>> The series is based on 5.8.0-rc3 and is intended for Jason Gunthorpe's
>> hmm tree. These were originally part of a larger series:
>> https://lore.kernel.org/linux-mm/20200619215649.32297-1-rcampbell@nvidia.com/
>>
>> Changes in v3:
>> Replaced the HMM_PFN_P[MU]D flags with hmm_pfn_to_map_order() to
>> indicate the size of the CPU mapping.
>>
>> Changes in v2:
>> Make the hmm_range_fault() API changes into a separate series and add
>>    two output flags for PMD/PUD instead of a single compund page flag as
>>    suggested by Jason Gunthorpe.
>> Make the nouveau page table changes a separate patch as suggested by
>>    Ben Skeggs.
>> Only add support for 2MB nouveau mappings initially since changing the
>> 1:1 CPU/GPU page table size assumptions requires a bigger set of changes.
>> Rebase to 5.8.0-rc3.
>>
>> Ralph Campbell (5):
>>    nouveau/hmm: fault one page at a time
>>    mm/hmm: add hmm_mapping order
>>    nouveau: fix mapping 2MB sysmem pages
>>    nouveau/hmm: support mapping large sysmem pages
>>    hmm: add tests for HMM_PFN_PMD flag
> 
> Applied to hmm.git.
> 
> I edited the comment for hmm_pfn_to_map_order() and added a function
> to compute the field.
> 
> Thanks,
> Jason

Looks good, thanks.