[xen staging] x86/mm: ensure L2 is always freed if empty

[patchbot@xxxxxxx]

commit a6dba2761e2ecaa7ffc3d3bb3c85685d232bbe68
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Thu Oct 31 12:43:10 2024 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Oct 31 12:43:10 2024 +0100

    x86/mm: ensure L2 is always freed if empty
    
    The current logic in modify_xen_mappings() allows for fully empty L2 tables 
to
    not be freed and unhooked from the parent L3 if the last L2 slot is not
    populated.
    
    Ensure that even when an L2 slot is empty the logic to check whether the 
whole
    L2 can be removed is not skipped.
    
    Fixes: 4376c05c3113 ('x86-64: use 1GB pages in 1:1 mapping if available')
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/mm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index d537a799bc..0f53dcebad 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5717,7 +5717,7 @@ int modify_xen_mappings(unsigned long s, unsigned long e, 
unsigned int nf)
 
             v += 1UL << L2_PAGETABLE_SHIFT;
             v &= ~((1UL << L2_PAGETABLE_SHIFT) - 1);
-            continue;
+            goto check_l3;
         }
 
         if ( l2e_get_flags(*pl2e) & _PAGE_PSE )
--
generated by git-patchbot for /home/xen/git/xen.git#staging