Re: [Xen-devel] [PATCH 0/3] [RFC] User-space grant table device

[Derek Murray <Derek.Murray@xxxxxxxxxxxx>]

On 21 Mar 2007, at 04:32, Isaku Yamahata wrote:
> This patch doesn't work on ia64 and ppc because they doesn't support
> GNTMAP_application_map which is x86 speicific. The flag doesn't make
> sense for ia64 and ppc. (When auto_translated_physmap_mode is enabled,
> GNTMAP_application_map isn't necessary.)
> Fortunately there was the similar issue in blktap. It was solved
> by utilizing auto_translated_physmap_mode.
Please forgive my ignorance of ia64 and ppc, as I don't have ready  
access to either for development. I based my work on the blktap  
driver, although there were some bits that I didn't understand.
blktap appears to map each grant into kernel space and, when not  
using auto-translated mode, into user space as well. If it is using  
auto-translated mode, then the grant is only mapped into the kernel.
Am I correct in thinking that the use of the VM_FOREIGN flag, plus  
the use of vm_private_data to store an array of struct page pointers,  
enables the pages to be mapped into user space using get_user_pages()  
(which is called by make_pages_present(), which is called by  
do_mmap_pgoff())? Or is it the call to vm_insert_page()?
> If it is diffucult for you to work on it (ia64 or ppc machine is  
> necessary),
> I'd like to do.
I'll have a try at adding the code to work in these cases, though I  
would appreciate your feedback on whether the changes are correct.
> Your goal seems to be to rewrite xen console daemon and xensotred.
> (and blktap if possible).
> They are very fundamental, so I want to resolve it in advance
> instead of finding/fixing the breakage after the commit.
Definitely!

Regards,

Derek Murray.



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