Re: [PATCH][RFC]: pte notifiers -- support for external page tables

[Rik van Riel <riel@redhat.com>]

Avi Kivity wrote:

> This sample patch adds a new mechanism, pte notifiers, that allows drivers
> to register an interest in a changes to ptes. Whenever Linux changes a
> pte, it will call a notifier to allow the driver to adjust the external
> page table and flush its tlb.
> 
> Note that only one notifier is implemented, ->clear(), but others should be
> similar.

This approach makes a lot of sense.

> diff --git a/mm/rmap.c b/mm/rmap.c
> index 41ac397..3f61d38 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -682,6 +682,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
>  	}
>  
>  	/* Nuke the page table entry. */
> +	pte_notifier_call(vma, clear, address);
>  	flush_cache_page(vma, address, page_to_pfn(page));
>  	pteval = ptep_clear_flush(vma, address, pte);

If you want this to be useful to Infiniband, you should probably
also hook up do_wp_page() in mm/memory.c, where a page table can
be pointed to another page.

Probably the code in mm/mremap.c will need to be hooked up too.

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