[PATCH v7 08/14] xen/page_alloc: introduce preserved page flags macro

[Carlo Nonato <carlo.nonato@minervasys.tech>]

PGC_static and PGC_extra needs to be preserved when assigning a page.
Define a new macro that groups those flags and use it instead of or'ing
every time.

To make preserved flags even more meaningful, they are kept also when
switching state in mark_page_free().

Signed-off-by: Carlo Nonato <carlo.nonato@minervasys.tech>
---
v7:
- PGC_preserved used also in mark_page_free()
v6:
- preserved_flags renamed to PGC_preserved
- PGC_preserved is used only in assign_pages()
v5:
- new patch
---
 xen/common/page_alloc.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index c38edb9a58..6a98d9013f 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -158,6 +158,8 @@
 #define PGC_static 0
 #endif
 
+#define PGC_preserved (PGC_extra | PGC_static)
+
 #ifndef PGT_TYPE_INFO_INITIALIZER
 #define PGT_TYPE_INFO_INITIALIZER 0
 #endif
@@ -1424,11 +1426,11 @@ static bool mark_page_free(struct page_info *pg, mfn_t mfn)
     {
     case PGC_state_inuse:
         BUG_ON(pg->count_info & PGC_broken);
-        pg->count_info = PGC_state_free;
+        pg->count_info = PGC_state_free | (pg->count_info & PGC_preserved);
         break;
 
     case PGC_state_offlining:
-        pg->count_info = (pg->count_info & PGC_broken) |
+        pg->count_info = (pg->count_info & (PGC_broken | PGC_preserved)) |
                          PGC_state_offlined;
         pg_offlined = true;
         break;
@@ -2363,7 +2365,7 @@ int assign_pages(
 
         for ( i = 0; i < nr; i++ )
         {
-            ASSERT(!(pg[i].count_info & ~(PGC_extra | PGC_static)));
+            ASSERT(!(pg[i].count_info & ~PGC_preserved));
             if ( pg[i].count_info & PGC_extra )
                 extra_pages++;
         }
@@ -2423,7 +2425,7 @@ int assign_pages(
         page_set_owner(&pg[i], d);
         smp_wmb(); /* Domain pointer must be visible before updating refcnt. */
         pg[i].count_info =
-            (pg[i].count_info & (PGC_extra | PGC_static)) | PGC_allocated | 1;
+            (pg[i].count_info & PGC_preserved) | PGC_allocated | 1;
 
         page_list_add_tail(&pg[i], page_to_list(d, &pg[i]));
     }
-- 
2.34.1