xen/swiotlb: remember having called xen_create_contiguous_region()

xen/swiotlb: remember having called xen_create_contiguous_region()

Instead of always calling xen_destroy_contiguous_region() in case the
memory is DMA-able for the used device, do so only in case it has been
made DMA-able via xen_create_contiguous_region() before.

This will avoid a lot of xen_destroy_contiguous_region() calls for
64-bit capable devices.

As the memory in question is owned by swiotlb-xen the PG_owner_priv_1
flag of the first allocated page can be used for remembering.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
(cherry picked from commit b877ac9815a8fe7e5f6d7fdde3dc34652408840a)
Orabug: 30141778
Signed-off-by: Brian Maly <brian.maly@oracle.com>
Conflicts:
  PF_NO_COMPOUND is not used for PAGEFLAG() in uek4

Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Joe Jin <joe.jin@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>