From: Andres Lagar-Cavilla <andres@lagarcavilla.org>
Date: Thu, 24 Nov 2011 15:20:57 +0000 (+0000)
Subject: x86/mm/p2m: fix pod locking
X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/success//%22http:/www.example.com/cgi/success/?a=commitdiff_plain;h=85826188d83ea040c55cfe1e3d92d8626c3e3c3d;p=xen.git

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@lagarcavilla.org>
Acked-by: George Dunlap <george.dunlap@eu.citrix.com>
Acked-by: Tim Deegan <tim@xen.org>
Committed-by: Tim Deegan <tim@xen.org>
---

diff --git a/xen/arch/x86/mm/p2m-pod.c b/xen/arch/x86/mm/p2m-pod.c
index 49ee48f48a..098cacabbf 100644
--- a/xen/arch/x86/mm/p2m-pod.c
+++ b/xen/arch/x86/mm/p2m-pod.c
@@ -987,7 +987,6 @@ p2m_pod_demand_populate(struct p2m_domain *p2m, unsigned long gfn,
         set_p2m_entry(p2m, gfn_aligned, _mfn(0), PAGE_ORDER_2M,
                       p2m_populate_on_demand, p2m->default_access);
         audit_p2m(p2m, 1);
-        p2m_unlock(p2m);
         return 0;
     }
 
diff --git a/xen/arch/x86/mm/p2m-pt.c b/xen/arch/x86/mm/p2m-pt.c
index 7e48e7e3b4..d1ef744662 100644
--- a/xen/arch/x86/mm/p2m-pt.c
+++ b/xen/arch/x86/mm/p2m-pt.c
@@ -542,10 +542,11 @@ pod_retry_l3:
             /* The read has succeeded, so we know that mapping exists */
             if ( q != p2m_query )
             {
-                if ( !p2m_pod_demand_populate(p2m, gfn, PAGE_ORDER_1G, q) )
+                if ( !p2m_pod_check_and_populate(p2m, gfn,
+                                      (l1_pgentry_t *) &l3e, PAGE_ORDER_1G, q) )
                     goto pod_retry_l3;
                 p2mt = p2m_invalid;
-                printk("%s: Allocate 1GB failed!\n", __func__);
+                gdprintk(XENLOG_ERR, "%s: Allocate 1GB failed!\n", __func__);
                 goto out;
             }
             else
@@ -743,8 +744,10 @@ pod_retry_l3:
             {
                 if ( q != p2m_query )
                 {
-                    if ( !p2m_pod_demand_populate(p2m, gfn, PAGE_ORDER_1G, q) )
+                    if ( !p2m_pod_check_and_populate(p2m, gfn,
+                                      (l1_pgentry_t *) l3e, PAGE_ORDER_1G, q) )
                         goto pod_retry_l3;
+                    gdprintk(XENLOG_ERR, "%s: Allocate 1GB failed!\n", __func__);
                 }
                 else
                     *t = p2m_populate_on_demand;