Re: [Xen-devel] Re: Next steps with pv_ops for Xen

[Gerd Hoffmann <kraxel@xxxxxxxxxx>]

>> Alternatively, could we use the _PAGE_GNTTAB PTE flag that is used for
>> debugging? Indeed, if we did this, could be obviate the need for the
>> PTE-zapping hook, by instead catching the case where this flag is set,
>> and unmapping the grant implicitly?
> 
> Well, in the general case you don't have enough info to know which grant to
> release (a single page can be granted multiple times).

You'll also get the mm and the addr which should make it sufficiently
unique, so this looks like a doable approach to me.

ptep_get_and_clear_full() in include/asm-x86/pgtable_32.h needs to be
changed take care, but that should be possible to do and the change is
local to x86 paravirt_ops, which looks much better to me than touching
generic mm code.

cheers,
  Gerd



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