[PATCH] RFC: dma-buf: Require VM_SPECIAL vma for mmap

[Jason Gunthorpe]

On Thu, Feb 04, 2021 at 08:59:59PM +0100, Daniel Vetter wrote:

> So I think just checking for VM_PFNMAP after the vma is set up should
> be enough to guarantee we'll only have pte_special ptes in there,
> ever. But I'm not sure, this stuff all isn't really documented much
> and the code is sometimes a maze (to me at least).

Yes, that makes sense. VM_PFNMAP and !VM_MIXEDMAP seems like the right
check after the VMA is populated

But how do you stuff special pfns into a VMA outside the fault
handler?

Jason