[PATCH 3/4] mm: simplify device private page handling in hmm_range_fault

[Ralph Campbell]

On 3/17/20 12:34 AM, Christoph Hellwig wrote:
> On Mon, Mar 16, 2020 at 03:49:51PM -0700, Ralph Campbell wrote:
>> On 3/16/20 12:32 PM, Christoph Hellwig wrote:
>>> Remove the code to fault device private pages back into system memory
>>> that has never been used by any driver.  Also replace the usage of the
>>> HMM_PFN_DEVICE_PRIVATE flag in the pfns array with a simple
>>> is_device_private_page check in nouveau.
>>>
>>> Signed-off-by: Christoph Hellwig <hch at lst.de>
>>
>> Getting rid of HMM_PFN_DEVICE_PRIVATE seems reasonable to me since a driver can
>> look at the struct page but what if a driver needs to fault in a page from
>> another device's private memory? Should it call handle_mm_fault()?
> 
> Obviously no driver cared for that so far.  Once we have test cases
> for that and thus testable code we can add code to fault it in from
> hmm_vma_handle_pte.
> 

I'm OK with the series. I think I would have been less confused if I looked at
patch 4 then 3.