[PATCH 2/2] mm: remove device private page support from hmm_range_fault

[Christoph Hellwig]

On Mon, Mar 16, 2020 at 07:49:35PM +0100, Christoph Hellwig wrote:
> On Mon, Mar 16, 2020 at 11:42:19AM -0700, Ralph Campbell wrote:
> >
> > On 3/16/20 10:52 AM, Christoph Hellwig wrote:
> >> No driver has actually used properly wire up and support this feature.
> >> There is various code related to it in nouveau, but as far as I can tell
> >> it never actually got turned on, and the only changes since the initial
> >> commit are global cleanups.
> >
> > This is not actually true. OpenCL 2.x does support SVM with nouveau and
> > device private memory via clEnqueueSVMMigrateMem().
> > Also, Ben Skeggs has accepted a set of patches to map GPU memory after being
> > migrated and this change would conflict with that.
> 
> Can you explain me how we actually invoke this code?
> 
> For that we'd need HMM_PFN_DEVICE_PRIVATE NVIF_VMM_PFNMAP_V0_VRAM
> set in ->pfns before calling hmm_range_fault, which isn't happening.

Ok, looks like the fault side is unused, but we need to keep the
non-fault path in place.  I'll fix up the patch.