Re: chasing the four level page table

[Andi Kleen]

hpa@xxxxxxxxx (H. Peter Anvin) writes:
>
> There seems to be at least two classes of device drivers -- graphics
> and RDMA -- which have a genuine need to DMA user pages, after
> appropriate locking, of course.

And block devices with O_DIRECT and network devices. We supported that
fine for years with get_user_pages.

The issue with DRM is just that it does something more different:

it wants to get at a AGP page outside get_user_pages doesn't work for
this because the AGP hole is often outside mem_map. For that a 
nice helper is missing.

I'm not 100% we really want a helper because it's rather obscure
requirement, unlikely to be useful for others, and it may be better 
to keep it in DRM.

-Andi
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