Don't unshadow when the shadow l2 is the current used shadow table.

Otherwise, when destroying the domain, if the current sl2 is unpinned
then the shadow page will be freed without accquire the shadow_lock.
This may also improve the performance due to avoiding uncessary
unshadow.

Signed-off-by: Xiaofeng Ling <xiaofeng.ling@intel.com>

diff --git a/xen/arch/x86/shadow.c b/xen/arch/x86/shadow.c
index d6c052428e8e75a9dc4b487937848aceb4254609..c8a9f1eb0277543c9fa9d344f652655c9a2d9fc2 100644 (file)
--- a/xen/arch/x86/shadow.c
+++ b/xen/arch/x86/shadow.c
@@ -1450,6 +1450,7 @@ static int resync_all(struct domain *d, u32 stype)
     int changed;
     u32 min_max_shadow, min_max_snapshot;
     int min_shadow, max_shadow, min_snapshot, max_snapshot;
+    struct vcpu *v;
 
     ASSERT(shadow_lock_is_acquired(d));
 
@@ -1739,6 +1740,9 @@ static int resync_all(struct domain *d, u32 stype)
 
         if ( unlikely(unshadow) )
         {
+            for_each_vcpu(d, v)
+                if(smfn == pagetable_get_pfn(v->arch.shadow_table))
+                    return need_flush;
             perfc_incrc(unshadow_l2_count);
             shadow_unpin(smfn);
 #if CONFIG_PAGING_LEVELS == 2

diff --git a/xen/arch/x86/shadow32.c b/xen/arch/x86/shadow32.c
index 298fdb1a5d8f0bd82e21b5c02fa2204eb473ef66..7d517ec3903541c862aca83696364b4341b2958c 100644 (file)
--- a/xen/arch/x86/shadow32.c
+++ b/xen/arch/x86/shadow32.c
@@ -2326,6 +2326,7 @@ static int resync_all(struct domain *d, u32 stype)
     int changed;
     u32 min_max_shadow, min_max_snapshot;
     int min_shadow, max_shadow, min_snapshot, max_snapshot;
+    struct vcpu *v;
 
     ASSERT(shadow_lock_is_acquired(d));
 
@@ -2527,6 +2528,9 @@ static int resync_all(struct domain *d, u32 stype)
 
         if ( unlikely(unshadow) )
         {
+            for_each_vcpu(d, v)
+                if(smfn == pagetable_get_pfn(v->arch.shadow_table))
+                    return need_flush;
             perfc_incrc(unshadow_l2_count);
             shadow_unpin(smfn);
             if ( unlikely(shadow_mode_external(d)) )