[Xen-changelog] [xen-unstable] x86/mm: fix EPT PoD locking to match the normal p2m case.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Tim Deegan <Tim.Deegan@xxxxxxxxxx>
# Date 1294933573 0
# Node ID b01ef59c8c805df751a8f6ae63cdd5c6a4565255
# Parent  54e91dcae649e23fd267d7afe623fbd52b1b4283
x86/mm: fix EPT PoD locking to match the normal p2m case.

This recursive-locking bug was fixed in the main p2m code in
20269:fd3d5d66c446 (in October 2009) but has lurked unseen in
the EPT side since then.  Copy the fix across.

Signed-off-by: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
---
 xen/arch/x86/mm/hap/p2m-ept.c |   21 ++++++++++++++-------
 1 files changed, 14 insertions(+), 7 deletions(-)

diff -r 54e91dcae649 -r b01ef59c8c80 xen/arch/x86/mm/hap/p2m-ept.c
--- a/xen/arch/x86/mm/hap/p2m-ept.c     Thu Jan 13 15:38:48 2011 +0000
+++ b/xen/arch/x86/mm/hap/p2m-ept.c     Thu Jan 13 15:46:13 2011 +0000
@@ -45,19 +45,26 @@ static int ept_pod_check_and_populate(st
                                       ept_entry_t *entry, int order,
                                       p2m_query_t q)
 {
+    /* Only take the lock if we don't already have it.  Otherwise it
+     * wouldn't be safe to do p2m lookups with the p2m lock held */
+    int do_locking = !p2m_locked_by_me(p2m);
     int r;
-    p2m_lock(p2m);
+
+    if ( do_locking )
+        p2m_lock(p2m);
 
     /* Check to make sure this is still PoD */
     if ( entry->sa_p2mt != p2m_populate_on_demand )
     {
+        if ( do_locking )
+            p2m_unlock(p2m);
+        return 0;
+    }
+
+    r = p2m_pod_demand_populate(p2m, gfn, order, q);
+
+    if ( do_locking )
         p2m_unlock(p2m);
-        return 0;
-    }
-
-    r = p2m_pod_demand_populate(p2m, gfn, order, q);
-
-    p2m_unlock(p2m);
 
     return r;
 }

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-changelog