[xen staging] xen/page_alloc: introduce preserved page flags macro

[patchbot@xxxxxxx]

commit b527a27e17886328ef26a856cb0a50a606330c29
Author:     Carlo Nonato <carlo.nonato@xxxxxxxxxxxxxxx>
AuthorDate: Thu Dec 19 10:05:14 2024 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Dec 19 10:05:14 2024 +0100

    xen/page_alloc: introduce preserved page flags macro
    
    PGC_static and PGC_extra need to be preserved when assigning a page.
    Define a new macro that groups those flags and use it instead of or'ing
    every time.
    
    Signed-off-by: Carlo Nonato <carlo.nonato@xxxxxxxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/common/page_alloc.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 1f424333db..b76a03fd73 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -160,6 +160,10 @@
 #endif
 
 #define PGC_no_buddy_merge PGC_static
+/*
+ * Flags that are preserved in assign_pages() (and only there)
+ */
+#define PGC_preserved (PGC_extra | PGC_static)
 
 #ifndef PGT_TYPE_INFO_INITIALIZER
 #define PGT_TYPE_INFO_INITIALIZER 0
@@ -2384,7 +2388,7 @@ 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++;
         }
@@ -2444,7 +2448,7 @@ 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]));
     }
--
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