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, 9 insertions, 2 deletions

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index 3e276eb23d1b..c949923a5668 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -49,10 +49,17 @@ extern bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn);
 extern unsigned long set_phys_range_identity(unsigned long pfn_s,
 					     unsigned long pfn_e);
 
+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);
 extern int m2p_add_override(unsigned long mfn, struct page *page,
 			    struct gnttab_map_grant_ref *kmap_op);
+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);
 extern int m2p_remove_override(struct page *page,
-				struct gnttab_map_grant_ref *kmap_op);
+			       struct gnttab_map_grant_ref *kmap_op,
+			       unsigned long mfn);
 extern struct page *m2p_find_override(unsigned long mfn);
 extern unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn);
 
@@ -121,7 +128,7 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn)
 		pfn = m2p_find_override_pfn(mfn, ~0);
 	}
 
-	/* 
+	/*
 	 * pfn is ~0 if there are no entries in the m2p for mfn or if the
 	 * entry doesn't map back to the mfn and m2p_override doesn't have a
 	 * valid entry for it.