[PATCH v20210701 12/40] tools: unify type checking for data pfns in migration stream

[Olaf Hering <olaf@xxxxxxxxx>]

Introduce a helper which decides if a given pfn in the migration
stream is backed by memory.

This specifically deals with type XEN_DOMCTL_PFINFO_XALLOC, which was
a synthetic toolstack-only type used in Xen 4.2 to 4.5. It indicated a
dirty page on the sending side for which no data will be send in the
initial iteration.

No change in behavior intended.

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
---
 tools/libs/saverestore/common.h  | 17 +++++++++++++++++
 tools/libs/saverestore/restore.c |  5 ++---
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/tools/libs/saverestore/common.h b/tools/libs/saverestore/common.h
index 07c506360c..fa242e808d 100644
--- a/tools/libs/saverestore/common.h
+++ b/tools/libs/saverestore/common.h
@@ -500,6 +500,23 @@ static inline bool sr_is_known_page_type(xen_pfn_t type)
     return ret;
 }
 
+static inline bool page_type_to_populate(uint32_t type)
+{
+    bool ret;
+
+    switch (type)
+    {
+    case XEN_DOMCTL_PFINFO_XTAB:
+    case XEN_DOMCTL_PFINFO_BROKEN:
+        ret = false;
+        break;
+    case XEN_DOMCTL_PFINFO_XALLOC:
+    default:
+        ret = true;
+        break;
+    }
+    return ret;
+}
 #endif
 /*
  * Local variables:
diff --git a/tools/libs/saverestore/restore.c b/tools/libs/saverestore/restore.c
index 324b9050e2..477b7527a1 100644
--- a/tools/libs/saverestore/restore.c
+++ b/tools/libs/saverestore/restore.c
@@ -152,9 +152,8 @@ int populate_pfns(struct xc_sr_context *ctx, unsigned int 
count,
 
     for ( i = 0; i < count; ++i )
     {
-        if ( (!types || (types &&
-                         (types[i] != XEN_DOMCTL_PFINFO_XTAB &&
-                          types[i] != XEN_DOMCTL_PFINFO_BROKEN))) &&
+        if ( (!types ||
+              (types && page_type_to_populate(types[i]) == true)) &&
              !pfn_is_populated(ctx, original_pfns[i]) )
         {
             rc = pfn_set_populated(ctx, original_pfns[i]);