[RFC] mm/hmm: pass mmu_notifier_range to sync_cpu_device_pagetables

[Jason Gunthorpe]

On Fri, Jun 07, 2019 at 05:14:52PM -0700, Ralph Campbell wrote:
> HMM defines its own struct hmm_update which is passed to the
> sync_cpu_device_pagetables() callback function. This is
> sufficient when the only action is to invalidate. However,
> a device may want to know the reason for the invalidation and
> be able to see the new permissions on a range, update device access
> rights or range statistics. Since sync_cpu_device_pagetables()
> can be called from try_to_unmap(), the mmap_sem may not be held
> and find_vma() is not safe to be called.
> Pass the struct mmu_notifier_range to sync_cpu_device_pagetables()
> to allow the full invalidation information to be used.
> 
> Signed-off-by: Ralph Campbell <rcampbell at nvidia.com>
> ---
> 
> I'm sending this out now since we are updating many of the HMM APIs
> and I think it will be useful.

I agree with CH that struct hmm_update seems particularly pointless
and we really should just use mmu_notifier_range directly.

We need to find out from the DRM folks if we can merge this kind of
stuff through hmm.git and then resolve any conflicts that might arise
in DRM tree or in nouveau tree?

But I would like to see this patch go in this cycle, thanks

Jason