gnttab: simplify page copying/clearing

... by making {copy,clear}_domain_page() available also on other than
x86.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/domain_page.c
+++ b/xen/arch/x86/domain_page.c
@@ -230,24 +230,6 @@ void unmap_domain_page(const void *ptr)
     local_irq_restore(flags);
 }
 
-void clear_domain_page(unsigned long mfn)
-{
-    void *ptr = map_domain_page(mfn);
-
-    clear_page(ptr);
-    unmap_domain_page(ptr);
-}
-
-void copy_domain_page(unsigned long dmfn, unsigned long smfn)
-{
-    const void *src = map_domain_page(smfn);
-    void *dst = map_domain_page(dmfn);
-
-    copy_page(dst, src);
-    unmap_domain_page(dst);
-    unmap_domain_page(src);
-}
-
 int mapcache_domain_init(struct domain *d)
 {
     struct mapcache_domain *dcache = &d->arch.pv_domain.mapcache;
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -1712,7 +1712,6 @@ gnttab_transfer(
         if ( (1UL << (max_bitsize - PAGE_SHIFT)) <= mfn )
         {
             struct page_info *new_page;
-            void *sp, *dp;
 
             new_page = alloc_domheap_page(e, MEMF_no_owner |
                                              MEMF_bits(max_bitsize));
@@ -1722,11 +1721,7 @@ gnttab_transfer(
                 goto unlock_and_copyback;
             }
 
-            sp = map_domain_page(mfn);
-            dp = __map_domain_page(new_page);
-            memcpy(dp, sp, PAGE_SIZE);
-            unmap_domain_page(dp);
-            unmap_domain_page(sp);
+            copy_domain_page(page_to_mfn(new_page), mfn);
 
             page->count_info &= ~(PGC_count_mask|PGC_allocated);
             free_domheap_page(page);
@@ -2520,7 +2515,7 @@ gnttab_set_version(XEN_GUEST_HANDLE_PARA
     /* Make sure there's no crud left over in the table from the
        old version. */
     for ( i = 0; i < nr_grant_frames(gt); i++ )
-        memset(gt->shared_raw[i], 0, PAGE_SIZE);
+        clear_page(gt->shared_raw[i]);
 
     /* Restore the first 8 entries (toolstack reserved grants) */
     if ( gt->gt_version != 0 && op.version == 1 )
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -1170,6 +1170,26 @@ long do_memory_op(unsigned long cmd, XEN
     return rc;
 }
 
+#ifdef CONFIG_DOMAIN_PAGE
+void clear_domain_page(unsigned long mfn)
+{
+    void *ptr = map_domain_page(mfn);
+
+    clear_page(ptr);
+    unmap_domain_page(ptr);
+}
+
+void copy_domain_page(unsigned long dmfn, unsigned long smfn)
+{
+    const void *src = map_domain_page(smfn);
+    void *dst = map_domain_page(dmfn);
+
+    copy_page(dst, src);
+    unmap_domain_page(dst);
+    unmap_domain_page(src);
+}
+#endif
+
 void destroy_ring_for_helper(
     void **_va, struct page_info *page)
 {
--- a/xen/include/asm-arm/page.h
+++ b/xen/include/asm-arm/page.h
@@ -264,6 +264,8 @@ static inline lpae_t mfn_to_xen_entry(un
 /* Actual cacheline size on the boot CPU. */
 extern size_t cacheline_bytes;
 
+#define copy_page(dp, sp) memcpy(dp, sp, PAGE_SIZE)
+
 /* Functions for flushing medium-sized areas.
  * if 'range' is large enough we might want to use model-specific
  * full-cache flushes. */