[xen stable-4.19] x86/mm: ensure L2 is always freed if empty

[patchbot@xxxxxxx]

commit 6a0ef94a8fcd7dfb041646e38840131a925f6d2e
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Mon Nov 25 12:03:23 2024 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Nov 25 12:03:23 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>
    master commit: 41c80496084aa3601230e01c3bc579a0a6d8359a
    master date: 2024-11-14 16:13:10 +0100
---
 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 07631067ae..d65cf9fa71 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5728,7 +5728,7 @@ 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#stable-4.19