On Tue, Mar 17, 2020 at 01:28:13PM +0100, Christoph Hellwig wrote: > On Tue, Mar 17, 2020 at 01:24:45PM +0100, Christoph Hellwig wrote: > > On Tue, Mar 17, 2020 at 09:15:36AM -0300, Jason Gunthorpe wrote: > > > > 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()? > > > > > > Isn't that what this series basically does? > > > > > > The dev_private_owner is set to the type of pgmap the device knows how > > > to handle, and everything else is automatically faulted for the > > > device. > > > > > > If the device does not know how to handle device_private then it sets > > > dev_private_owner to NULL and it never gets device_private pfns. > > > > > > Since the device_private pfn cannot be dma mapped, drivers must have > > > explicit support for them. > > > > No, with this series (and all actual callers before this series) > > we never fault in device private pages. > > IFF we want to fault it in we'd need something like this. But I'd > really prefer to see test cases for that first. In general I think hmm_range_fault should have a mode that is the same as get_user_pages in terms of when it returns a hard failure, and generates faults. AFAIK, GUP will fault in this case? I need this for making ODP use this API. ODP is the one that is highly likely to see other driver's device_private pages and must have them always fault to CPU. > diff --git a/mm/hmm.c b/mm/hmm.c > index b75b3750e03d..2884a3d11a1f 100644 > +++ b/mm/hmm.c > @@ -276,7 +276,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, > if (!fault && !write_fault) > return 0; > > - if (!non_swap_entry(entry)) > + if (!non_swap_entry(entry) || is_device_private_entry(entry)) > goto fault; Yes, OK, makes sense. I've been using v7 of Ralph's tester and it is working well - it has DEVICE_PRIVATE support so I think it can test this flow too. Ralph are you able? This hunk seems trivial enough to me, can we include it now? Thanks, Jason
