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, 32 insertions, 0 deletions

diff --git a/arch/arm/xen/p2m.c b/arch/arm/xen/p2m.c
index b31ee1b275b0..97baf4427817 100644
--- a/arch/arm/xen/p2m.c
+++ b/arch/arm/xen/p2m.c
@@ -146,6 +146,38 @@ unsigned long __mfn_to_pfn(unsigned long mfn)
 }
 EXPORT_SYMBOL_GPL(__mfn_to_pfn);
 
+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)
+{
+        int i;
+
+        for (i = 0; i < count; i++) {
+                if (map_ops[i].status)
+                        continue;
+                set_phys_to_machine(map_ops[i].host_addr >> PAGE_SHIFT,
+                                    map_ops[i].dev_bus_addr >> PAGE_SHIFT);
+        }
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
+
+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)
+{
+        int i;
+
+        for (i = 0; i < count; i++) {
+                set_phys_to_machine(unmap_ops[i].host_addr >> PAGE_SHIFT,
+                                    INVALID_P2M_ENTRY);
+        }
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
+
 bool __set_phys_to_machine_multi(unsigned long pfn,
                 unsigned long mfn, unsigned long nr_pages)
 {