RE: [PATCH 09/17] mm: export access_remote_vm() symbol

["Yu, Fenghua" <fenghua.yu@intel.com>]

Hi, Alistair,

> >> Alistair Popple <apopple@nvidia.com> writes:
> >> Lorenzo Stoakes <lstoakes@gmail.com> writes:
> >> > My concern is exposing something highly delicate _which accesses
> >> > remote mas a public API with implicit assumptions whose one and
> >> > only (core kernel) user treats with enormous caution. Even if this
> >> > iommu code were to use it correctly, we'd end up with an interface
> >> > which could be
> >> subject to real risks which other drivers may misuse.
> >>
> >> Ok, although I think making this an iommu specific wrapper taking a
> >> PASID rather than mm_struct would make the API more specific and less
> >> likely to be misused as the mm_count/users lifetime issues could be
> >> dealt with inside the core IOMMU code.
> >
> > The iommu specific wrapper still needs to call access_remote_vm()
> > which is in generic mm. We cannot avoid to export access_remote_vm(), right?
> 
> The wrapper still needs to call access_remote_vm(), but that doesn't imply
> access_remote_vm() needs to be exported. I think the logical place to put the
> wrapper would be in iommu-sva.c which isn't built as a module, so you would
> only have to EXPORT_SYMBOL_GPL the wrapper and not access_remote_vm().

This looks better than exporting access_remote_vm(). I will remove this patch
and write the IOMMU wrapper to call access_remote_vm() in v2.

Thanks.

-Fenghua