xen-gntdev: Support mapping in HVM domains

HVM does not allow direct PTE modification, so instead we request
that Xen change its internal p2m mappings on the allocated pages and
map the memory into userspace normally.

Note:
The HVM path for map and unmap is slightly different: HVM keeps the pages
mapped until the area is deleted, while the PV case (use_ptemod being true)
must unmap them when userspace unmaps the range. In the normal use case,
this makes no difference to users since unmap time is deletion time.

[v2: Expanded commit descr.]
Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 9ef54ebc1194..9428ced04807 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -458,6 +458,9 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
         if (ret)
                 return ret;
 
+        if (xen_feature(XENFEAT_auto_translated_physmap))
+                return ret;
+
         for (i = 0; i < count; i++) {
                 /* m2p override only supported for GNTMAP_contains_pte mappings */
                 if (!(map_ops[i].flags & GNTMAP_contains_pte))
@@ -483,6 +486,9 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
         if (ret)
                 return ret;
 
+        if (xen_feature(XENFEAT_auto_translated_physmap))
+                return ret;
+
         for (i = 0; i < count; i++) {
                 ret = m2p_remove_override(pages[i]);
                 if (ret)