Xen devel - Apr 2012 - [question]: __gnttab_map_grant_ref() and iommu

Hi,

I''m not able to figure why __gnttab_map_grant_ref() does PV iommu
mappings for GNTMAP_host_map. Should it not check for GNTMAP_device_map
and do for those only?

thanks,
Mukesh

On Wed, 2012-04-04 at 03:14 +0100, Mukesh Rathor wrote:
> I''m not able to figure why __gnttab_map_grant_ref() does PV iommu
> mappings for GNTMAP_host_map. Should it not check for GNTMAP_device_map
> and do for those only?
I don''t know but perhaps it is because when the backend maps a foreign
page there is a reasonably high chance that it is eventually going to
end up passing that page to a hardware device (e.g. a physical NIC or
disk controller) for DMA and therefore the mapping must be reflected in
the IOMMU.

Ian.