Xen devel - Nov 2011 - [PATCH] mem_event: check capabilities only once

# HG changeset patch
# User Olaf Hering <olaf@aepfle.de>
# Date 1320773602 -3600
# Node ID a7e49740fbfe3a4ec0a21186e2a4c579a30e0838
# Parent  c681dd5aecf3da3c6fd0e4d8a760a9cd18617033
mem_event: check capabilities only once

It is not required to check the system capabilities during every domctl.
Rearrange the code to check them only once.

Signed-off-by: Olaf Hering <olaf@aepfle.de>

diff -r c681dd5aecf3 -r a7e49740fbfe xen/arch/x86/mm/mem_event.c
--- a/xen/arch/x86/mm/mem_event.c
+++ b/xen/arch/x86/mm/mem_event.c
@@ -253,32 +253,35 @@ int mem_event_domctl(struct domain *d, x
     case XEN_DOMCTL_MEM_EVENT_OP_PAGING:
     {
         struct mem_event_domain *med = &d->mem_paging;
-        struct p2m_domain *p2m = p2m_get_hostp2m(d);
-        rc = -ENODEV;
-        /* Only HAP is supported */
-        if ( !hap_enabled(d) )
-            break;
-
-        /* Currently only EPT is supported */
-        if ( boot_cpu_data.x86_vendor != X86_VENDOR_INTEL )
-            break;
-
-        rc = -EXDEV;
-        /* Disallow paging in a PoD guest */
-        if ( p2m->pod.entry_count )
-            break;
+        rc = -EINVAL;
 
         switch( mec->op )
         {
         case XEN_DOMCTL_MEM_EVENT_OP_PAGING_ENABLE:
         {
+            struct p2m_domain *p2m = p2m_get_hostp2m(d);
+            rc = -ENODEV;
+            /* Only HAP is supported */
+            if ( !hap_enabled(d) )
+                break;
+
+            /* Currently only EPT is supported */
+            if ( boot_cpu_data.x86_vendor != X86_VENDOR_INTEL )
+                break;
+
+            rc = -EXDEV;
+            /* Disallow paging in a PoD guest */
+            if ( p2m->pod.entry_count )
+                break;
+
             rc = mem_event_enable(d, mec, med);
         }
         break;
 
         case XEN_DOMCTL_MEM_EVENT_OP_PAGING_DISABLE:
         {
-            rc = mem_event_disable(med);
+            if ( med->ring_page )
+                rc = mem_event_disable(med);
         }
         break;
 
@@ -295,26 +298,29 @@ int mem_event_domctl(struct domain *d, x
     case XEN_DOMCTL_MEM_EVENT_OP_ACCESS: 
     {
         struct mem_event_domain *med = &d->mem_access;
-        rc = -ENODEV;
-        /* Only HAP is supported */
-        if ( !hap_enabled(d) )
-            break;
-
-        /* Currently only EPT is supported */
-        if ( boot_cpu_data.x86_vendor != X86_VENDOR_INTEL )
-            break;
+        rc = -EINVAL;
 
         switch( mec->op )
         {
         case XEN_DOMCTL_MEM_EVENT_OP_ACCESS_ENABLE:
         {
+            rc = -ENODEV;
+            /* Only HAP is supported */
+            if ( !hap_enabled(d) )
+                break;
+
+            /* Currently only EPT is supported */
+            if ( boot_cpu_data.x86_vendor != X86_VENDOR_INTEL )
+                break;
+
             rc = mem_event_enable(d, mec, med);
         }
         break;
 
         case XEN_DOMCTL_MEM_EVENT_OP_ACCESS_DISABLE:
         {
-            rc = mem_event_disable(&d->mem_access);
+            if ( med->ring_page )
+                rc = mem_event_disable(&d->mem_access);
         }
         break;
 

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