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

[patchbot@xxxxxxx]

commit 41c80496084aa3601230e01c3bc579a0a6d8359a
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Thu Nov 14 16:13:10 2024 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Nov 14 16:13:10 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 b9a2234b53..5d7e8d7871 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5989,7 +5989,7 @@ 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#master