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

[Alistair Popple <apopple@nvidia.com>]

"Yu, Fenghua" <fenghua.yu@intel.com> writes:

> 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().

> Are you saying the iommu specific wrapper doesn't need to the mm code?
>
> Thanks.
>
> -Fenghua