[Xen-devel] [PATCH 2 of 8] x86/mm: Fix p2m teardown locking

[Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>]

 xen/arch/x86/mm/p2m.c |  4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)


Holding the p2m lock during a p2m teardown, while unsharing entries pointing to
shared frames, causes a locking inversion and deadlock panic.

Signed-off-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>

diff -r 143e4982c9bf -r 2e7c77585adb xen/arch/x86/mm/p2m.c
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -343,8 +343,6 @@ void p2m_teardown(struct p2m_domain *p2m
     if (p2m == NULL)
         return;
 
-    p2m_lock(p2m);
-
 #ifdef __x86_64__
     for ( gfn=0; gfn < p2m->max_mapped_pfn; gfn++ )
     {
@@ -358,6 +356,8 @@ void p2m_teardown(struct p2m_domain *p2m
     }
 #endif
 
+    p2m_lock(p2m);
+
     p2m->phys_table = pagetable_null();
 
     while ( (pg = page_list_remove_head(&p2m->pages)) )

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