[Xen-devel] grant table interface addition?

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

In order to be able to set some of the available bits in the pte resulting from
gnttab_set_map_op() (in particular PAGE_SPECIAL and possibly PAGE_IO),
it would seem necessary to extend the set of flags that can be passed to
that function. While the addition by itself is a simple operation, the question
is how to deal with backward compatibility here: Is there anything
preventing the guest kernel from setting the flags it wants manually after
Xen established the mapping, i.e. would Xen either disallow any modification
to such pte-s, or get confused by the pte not being identical to what it set
it to?

As to PAGE_IO, wouldn't it be appropriate to set this flag on pte-s created
with GNTMAP_device_map? Or is the name misleading me? I'm perhaps
confused by the fact that the use of this flag is not tied to granting iomem
pages...

Thanks, Jan


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