xen/grant-table: Refactor gnttab_[un]map_refs to avoid m2p_override

The grant mapping API does m2p_override unnecessarily: only gntdev needs it,
for blkback and future netback patches it just cause a lock contention, as
those pages never go to userspace. Therefore this series does the following:
- the bulk of the original function (everything after the mapping hypercall)
  is moved to arch-dependent set/clear_foreign_p2m_mapping
- the "if (xen_feature(XENFEAT_auto_translated_physmap))" branch goes to ARM
- therefore the ARM function could be much smaller, the m2p_override stubs
  could be also removed
- on x86 the set_phys_to_machine calls were moved up to this new funcion
  from m2p_override functions
- and m2p_override functions are only called when there is a kmap_ops param

It also removes a stray space from arch/x86/include/asm/xen/page.h.

Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
Suggested-by: Anthony Liguori <aliguori@amazon.com>
Suggested-by: David Vrabel <david.vrabel@citrix.com>
Suggested-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

1 files changed, 6 insertions, 9 deletions

diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h
index e0965abacb7d..cf4f3e867395 100644
--- a/arch/arm/include/asm/xen/page.h
+++ b/arch/arm/include/asm/xen/page.h
@@ -97,16 +97,13 @@ static inline pte_t *lookup_address(unsigned long address, unsigned int *level)
 	return NULL;
 }
 
-static inline int m2p_add_override(unsigned long mfn, struct page *page,
-		struct gnttab_map_grant_ref *kmap_op)
-{
-	return 0;
-}
+extern int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
+				   struct gnttab_map_grant_ref *kmap_ops,
+				   struct page **pages, unsigned int count);
 
-static inline int m2p_remove_override(struct page *page, bool clear_pte)
-{
-	return 0;
-}
+extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
+				     struct gnttab_map_grant_ref *kmap_ops,
+				     struct page **pages, unsigned int count);
 
 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn);
 bool __set_phys_to_machine_multi(unsigned long pfn, unsigned long mfn,