[xen staging] xen/page_alloc: introduce page flag to stop buddy merging

[patchbot@xxxxxxx]

commit f5c2b6da26d9becd5a1a03fcd3e5c950301030a2
Author:     Carlo Nonato <carlo.nonato@xxxxxxxxxxxxxxx>
AuthorDate: Thu Mar 21 09:47:21 2024 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Mar 21 09:47:21 2024 +0100

    xen/page_alloc: introduce page flag to stop buddy merging
    
    Add a new PGC_no_buddy_merge flag that prevents the buddy algorithm in
    free_heap_pages() from merging pages that have it set. As of now, only
    PGC_static has this feature, but future work can extend it easier than
    before.
    
    Suggested-by: Jan Beulich <jbeulich@xxxxxxxx>
    Signed-off-by: Carlo Nonato <carlo.nonato@xxxxxxxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/common/page_alloc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 97788a52a7..a1c57fe1d9 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -158,6 +158,7 @@
 #endif
 
 #define PGC_preserved (PGC_extra | PGC_static)
+#define PGC_no_buddy_merge PGC_static
 
 #ifndef PGT_TYPE_INFO_INITIALIZER
 #define PGT_TYPE_INFO_INITIALIZER 0
@@ -1503,7 +1504,7 @@ static void free_heap_pages(
             /* Merge with predecessor block? */
             if ( !mfn_valid(page_to_mfn(predecessor)) ||
                  !page_state_is(predecessor, free) ||
-                 (predecessor->count_info & PGC_static) ||
+                 (predecessor->count_info & PGC_no_buddy_merge) ||
                  (PFN_ORDER(predecessor) != order) ||
                  (page_to_nid(predecessor) != node) )
                 break;
@@ -1527,7 +1528,7 @@ static void free_heap_pages(
             /* Merge with successor block? */
             if ( !mfn_valid(page_to_mfn(successor)) ||
                  !page_state_is(successor, free) ||
-                 (successor->count_info & PGC_static) ||
+                 (successor->count_info & PGC_no_buddy_merge) ||
                  (PFN_ORDER(successor) != order) ||
                  (page_to_nid(successor) != node) )
                 break;
--
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