[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] grant table interface addition?
On 30/10/08 14:06, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote: > 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? I think mod_l1_entry() would allow this since it does no validation unless the mapping or PRESENT/RW change. Direct page-table writing won't work as it happens since it will want to get_page() which of course won't work on a foreign page. It could be given the same fast path as mod_l1_entry(), of course. > 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... The idea was that this would grant-map pages into an iommu. Really it's not actually been used, but GNTMAP_device_map doesn't cause mappings to appear in host page tables. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
|
Lists.xenproject.org is hosted with RackSpace, monitoring our |