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SubjectRe: User switchable HW mappings & cie
Date
Hi all,

On Monday, 9. October 2006 13:51, Benjamin Herrenschmidt wrote:
> > One problem that occurs is that the rule for ptes with non-backing
> > struct pages
> > Which I think was introduced in 2.6.16:
> >
> > pfn_of_page == vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT)
> >
> > cannot be honored, at least not with the DRM memory manager, since the
> > graphics object will be associated with a vma and not the underlying
> > physical address. User space will have vma->vm_pgoff as a handle to the
> > object, which may move around in graphics memory.
>
> That's a problem with VM_PFNMAP set indeed. get_user_pages() is a
> non-issue with VM_IO set too but I'm not sure about other code path that
> might try to hit here... though I think we don't hit that if MAP_SHARED,
> Nick ?

Istn't this just a non-linear PFN mapping, you are describing here?

Nick:
Cant your new fault consolidation code handle that?
AFAICS your new .fault handler just gets the
vma and pgoff and install the matching PTE via install_THINGIE()
or vm_insert_THINGIE()

Or do I miss sth. here?


Regards

Ingo Oeser
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