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Re: Re: [Xen-devel] SetPageForeign in netback

Many thanks!
And that is, when tx, after the data page is sent by native Nic driver in dom0, 
the data page will be freed, then netif_page_release() called which indicates 
netback to unmap the page offered by domU, and moves on its tx response.

Is that so?
If so, how about a bad NIC driver which doen't call free_page() after sending 
data out of machine ?

and Why mmap_pages is allocated by 
can  mmap_pages be allocated by alloc_vm_area() and vmalloc_to_page() ??

Forgive my silly questions above please.

======= 2008-06-18 18:52:27 您在来信中写道:=======

>> hi,
>>  in netback init mmap_pages,
>>                SetPageForeign(page, netif_page_release);
>>  that is, page->index = netif_page_release
>>  while netif_page_release is a function.
>netif_page_release is a function, and therefore:
>page->index = netif_page_release
>will store netif_page_release function pointer in 'index'
>>  so what's the meaning of SetPageForeign?
>Setting a page foreign means that the page is owned by another domain,
>and that some care needs to be taken when freeing it.
>>  And when the function  netif_page_release() will be called?
>Whenever PageForeignDestructor is called (as it calls the destructor
>function stored in the 'index' field).
>PageForeignDestructor is called from:
>Hope this helps.
>Xen-devel mailing list

= = = = = = = = = = = = = = = = = = = =
Zang Hongyong

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