[v2,3/4] x86/setup: remove bootstrap_map_addr() usage of destroy_xen_mappings()

Commit Message

Roger Pau Monné Nov. 6, 2024, 12:29 p.m. UTC

bootstrap_map_addr() top level comment states that it doesn't indented to
remove the L2 tables, as the same L2 will be re-used to create further 2MB
mappings.  It's incorrect for the function to use destroy_xen_mappings() which
will free empty L2 tables.

Fix this by using map_pages_to_xen(), which does zap the page-table entries,
but does not free page-table structures even when empty.

Fixes: 4376c05c3113 ('x86-64: use 1GB pages in 1:1 mapping if available')
Signed-off-by: Roger Pau Monné <[e-mail]>
---
The fixes tag reflects the fact that if 4376c05c3113 freed the L2 correctly
when empty, it would have become obvious that bootstrap_map_addr() shouldn't be
using it if it wants to keep the L2.  4376c05c3113 should have switched
bootstrap_map_addr() to not use destroy_xen_mappings().
---
 xen/arch/x86/setup.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Patch

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 177f4024abca..815b8651ba79 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -456,7 +456,9 @@  static void *__init bootstrap_map_addr(paddr_t start, paddr_t end)
 
     if ( !end )
     {
-        destroy_xen_mappings(BOOTSTRAP_MAP_BASE, BOOTSTRAP_MAP_LIMIT);
+        map_pages_to_xen(BOOTSTRAP_MAP_BASE, INVALID_MFN,
+                         PFN_DOWN(map_cur - BOOTSTRAP_MAP_BASE),
+                         _PAGE_NONE);
         map_cur = BOOTSTRAP_MAP_BASE;
         return NULL;
     }