File 22744-ept-pod-locking.patch of Package xen

# HG changeset patch
# User Tim Deegan <Tim.Deegan@citrix.com>
# 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@citrix.com>

Index: xen-4.0.2-testing/xen/arch/x86/mm/hap/p2m-ept.c
===================================================================
--- xen-4.0.2-testing.orig/xen/arch/x86/mm/hap/p2m-ept.c
+++ xen-4.0.2-testing/xen/arch/x86/mm/hap/p2m-ept.c
@@ -37,19 +37,26 @@ 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(d->arch.p2m);
     int r;
-    p2m_lock(d->arch.p2m);
+
+    if ( do_locking )
+        p2m_lock(d->arch.p2m);
 
     /* Check to make sure this is still PoD */
     if ( entry->avail1 != p2m_populate_on_demand )
     {
-        p2m_unlock(d->arch.p2m);
+        if ( do_locking )
+            p2m_unlock(d->arch.p2m);
         return 0;
     }
 
     r = p2m_pod_demand_populate(d, gfn, order, q);
 
-    p2m_unlock(d->arch.p2m);
+    if ( do_locking )
+        p2m_unlock(d->arch.p2m);
 
     return r;
 }