[XEN PATCH v2 03/15] x86/p2m: guard altp2m routines

[Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>]

Initialize and bring down altp2m only when it is supported by the platform,
e.g. VMX. Also guard p2m_altp2m_propagate_change().
The puspose of that is the possiblity to disable altp2m support and exclude its
code from the build completely, when it's not supported by the target platform.

Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>
CC: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
---
 xen/arch/x86/mm/p2m-basic.c | 19 +++++++++++--------
 xen/arch/x86/mm/p2m-ept.c   |  2 +-
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/xen/arch/x86/mm/p2m-basic.c b/xen/arch/x86/mm/p2m-basic.c
index 8599bd15c6..90106997d7 100644
--- a/xen/arch/x86/mm/p2m-basic.c
+++ b/xen/arch/x86/mm/p2m-basic.c
@@ -126,13 +126,15 @@ int p2m_init(struct domain *d)
         return rc;
     }
 
-    rc = p2m_init_altp2m(d);
-    if ( rc )
+    if ( hvm_altp2m_supported() )
     {
-        p2m_teardown_hostp2m(d);
-        p2m_teardown_nestedp2m(d);
+        rc = p2m_init_altp2m(d);
+        if ( rc )
+        {
+            p2m_teardown_hostp2m(d);
+            p2m_teardown_nestedp2m(d);
+        }
     }
-
     return rc;
 }
 
@@ -195,11 +197,12 @@ void p2m_final_teardown(struct domain *d)
 {
     if ( is_hvm_domain(d) )
     {
+        if ( hvm_altp2m_supported() )
+            p2m_teardown_altp2m(d);
         /*
-         * We must tear down both of them unconditionally because
-         * we initialise them unconditionally.
+         * We must tear down nestedp2m unconditionally because
+         * we initialise it unconditionally.
          */
-        p2m_teardown_altp2m(d);
         p2m_teardown_nestedp2m(d);
     }
 
diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index f83610cb8c..d264df5b14 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -986,7 +986,7 @@ out:
     if ( is_epte_present(&old_entry) )
         ept_free_entry(p2m, &old_entry, target);
 
-    if ( entry_written && p2m_is_hostp2m(p2m) )
+    if ( entry_written && p2m_is_hostp2m(p2m) && hvm_altp2m_supported())
     {
         ret = p2m_altp2m_propagate_change(d, _gfn(gfn), mfn, order, p2mt, 
p2ma);
         if ( !rc )
-- 
2.25.1