[Xen-changelog] [xen-4.1-testing] x86/mm/p2m: fix pod locking

[Xen patchbot-4.1-testing <patchbot@xxxxxxx>]

# HG changeset patch
# User Tim Deegan <tim@xxxxxxx>
# Date 1323948019 0
# Node ID bb365e21314d2900fe1a4cf4e80ed1251a9c835b
# Parent  1c89f7d29fbb73e489b3f0a12138c1b372355575
x86/mm/p2m: fix pod locking

The path p2m-lookup -> p2m-pt->get_entry -> 1GB PoD superpage ->
pod_demand_populate ends in the pod code performing a p2m_set_entry with
no locks held (in order to split the 1GB superpage into 512 2MB ones)

Further, it calls p2m_unlock after that, which will break the spinlock.

This patch attempts to fix that.

Signed-off-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
Acked-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
Acked-by: Tim Deegan <tim@xxxxxxx>
xen-unstable changeset:   24189:7da681c490e0
xen-unstable date:        Thu Nov 24 15:20:57 2011 +0000
---


diff -r 1c89f7d29fbb -r bb365e21314d xen/arch/x86/mm/p2m.c
--- a/xen/arch/x86/mm/p2m.c     Thu Dec 08 16:50:28 2011 +0000
+++ b/xen/arch/x86/mm/p2m.c     Thu Dec 15 11:20:19 2011 +0000
@@ -1244,7 +1244,6 @@
         set_p2m_entry(p2m, gfn_aligned, _mfn(POPULATE_ON_DEMAND_MFN), 9,
                       p2m_populate_on_demand, p2m->default_access);
         audit_p2m(p2m, 1);
-        p2m_unlock(p2m);
         return 0;
     }
 
@@ -1602,7 +1601,8 @@
             {
                 if ( q != p2m_query )
                 {
-                    if ( !p2m_pod_demand_populate(p2m, gfn, 18, q) )
+                    if ( !p2m_pod_check_and_populate(p2m, gfn,
+                              (l1_pgentry_t *) &l3e, 18, q) )
                         goto pod_retry_l3;
                 }
                 else
@@ -1733,7 +1733,8 @@
                 /* The read has succeeded, so we know that mapping exists */
                 if ( q != p2m_query )
                 {
-                    if ( !p2m_pod_demand_populate(p2m, gfn, 18, q) )
+                    if ( !p2m_pod_check_and_populate(p2m, gfn,
+                              (l1_pgentry_t *) &l3e, 18, q) )
                         goto pod_retry_l3;
                     p2mt = p2m_invalid;
                     printk("%s: Allocate 1GB failed!\n", __func__);

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