Re: User switchable HW mappings & cie

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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?

	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?


Ingo Oeser
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