[PATCH 28/83] mm: Change timing of notification to IOMMUs about a page to be invalidated

[Andrew Morton]

On Fri, 11 Jul 2014 00:53:26 +0300 Oded Gabbay <oded.gabbay at gmail.com> wrote:

> From: Andrew Lewycky <Andrew.Lewycky at amd.com>
> 
> This patch changes the location of the mmu_notifier_invalidate_page function
> call inside try_to_unmap_one. The mmu_notifier_invalidate_page function
> call tells the IOMMU that a pgae should be invalidated.
> 
> The location is changed from after releasing the physical page to
> before releasing the physical page.
> 
> This change should prevent the bug that would occur in the
> (rare) case where the GPU attempts to access a page while the CPU
> attempts to swap out that page (or discard it if it is not dirty).

um OK, but what is the effect on all the other
mmu_notifier_ops.invalidate_page() implementations?

Please spell this out in full detail within the changelog and be sure
to cc the affected maintainers.