[Xen-devel] [PATCH] vm_event: make sure the domain is paused in key domctls

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

This patch pauses the domain for all writes through the 'ad'
pointer in monitor_domctl(), defers a domain_unpause() call until
after the CRs are updated for the MONITOR_EVENT_WRITE_CTRLREG
case, and makes sure that the domain is paused for both vm_event
enable and disable cases in vm_event_domctl().
Thanks go to Andrew Cooper for his review and suggestions.

Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
---
 xen/arch/x86/monitor.c | 18 ++++++++++--------
 xen/common/vm_event.c  | 18 ++++++++++++++++++
 2 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
index 7611f7b..bb1920a 100644
--- a/xen/arch/x86/monitor.c
+++ b/xen/arch/x86/monitor.c
@@ -80,7 +80,9 @@ int monitor_domctl(struct domain *d, struct 
xen_domctl_monitor_op *mop)
         return 0;
 
     case XEN_DOMCTL_MONITOR_OP_EMULATE_EACH_REP:
-        d->arch.mem_access_emulate_each_rep = !!mop->event;
+        domain_pause(d);
+        ad->mem_access_emulate_each_rep = !!mop->event;
+        domain_unpause(d);
         return 0;
     }
 
@@ -109,6 +111,8 @@ int monitor_domctl(struct domain *d, struct 
xen_domctl_monitor_op *mop)
         if ( rc )
             return rc;
 
+        domain_pause(d);
+
         if ( mop->u.mov_to_cr.sync )
             ad->monitor.write_ctrlreg_sync |= ctrlreg_bitmask;
         else
@@ -119,20 +123,18 @@ int monitor_domctl(struct domain *d, struct 
xen_domctl_monitor_op *mop)
         else
             ad->monitor.write_ctrlreg_onchangeonly &= ~ctrlreg_bitmask;
 
-        domain_pause(d);
-
         if ( !status )
             ad->monitor.write_ctrlreg_enabled |= ctrlreg_bitmask;
         else
             ad->monitor.write_ctrlreg_enabled &= ~ctrlreg_bitmask;
 
-        domain_unpause(d);
-
         if ( mop->u.mov_to_cr.index == VM_EVENT_X86_CR3 )
             /* Latches new CR3 mask through CR0 code */
             for_each_vcpu ( d, v )
                 hvm_update_guest_cr(v, 0);
 
+        domain_unpause(d);
+
         break;
     }
 
@@ -144,6 +146,8 @@ int monitor_domctl(struct domain *d, struct 
xen_domctl_monitor_op *mop)
         if ( rc )
             return rc;
 
+        domain_pause(d);
+
         if ( mop->op == XEN_DOMCTL_MONITOR_OP_ENABLE &&
              mop->u.mov_to_msr.extended_capture )
         {
@@ -154,7 +158,6 @@ int monitor_domctl(struct domain *d, struct 
xen_domctl_monitor_op *mop)
         } else
             ad->monitor.mov_to_msr_extended = 0;
 
-        domain_pause(d);
         ad->monitor.mov_to_msr_enabled = !status;
         domain_unpause(d);
         break;
@@ -196,9 +199,8 @@ int monitor_domctl(struct domain *d, struct 
xen_domctl_monitor_op *mop)
         if ( rc )
             return rc;
 
-        ad->monitor.guest_request_sync = mop->u.guest_request.sync;
-
         domain_pause(d);
+        ad->monitor.guest_request_sync = mop->u.guest_request.sync;
         ad->monitor.guest_request_enabled = !status;
         domain_unpause(d);
         break;
diff --git a/xen/common/vm_event.c b/xen/common/vm_event.c
index 28a7add..9d18c8d 100644
--- a/xen/common/vm_event.c
+++ b/xen/common/vm_event.c
@@ -624,15 +624,21 @@ int vm_event_domctl(struct domain *d, 
xen_domctl_vm_event_op_t *vec,
             if ( p2m->pod.entry_count )
                 break;
 
+            domain_pause(d);
             rc = vm_event_enable(d, vec, ved, _VPF_mem_paging,
                                  HVM_PARAM_PAGING_RING_PFN,
                                  mem_paging_notification);
+            domain_unpause(d);
         }
         break;
 
         case XEN_VM_EVENT_DISABLE:
             if ( ved->ring_page )
+            {
+                domain_pause(d);
                 rc = vm_event_disable(d, ved);
+                domain_unpause(d);
+            }
             break;
 
         case XEN_VM_EVENT_RESUME:
@@ -658,14 +664,20 @@ int vm_event_domctl(struct domain *d, 
xen_domctl_vm_event_op_t *vec,
         switch( vec->op )
         {
         case XEN_VM_EVENT_ENABLE:
+            domain_pause(d);
             rc = vm_event_enable(d, vec, ved, _VPF_mem_access,
                                  HVM_PARAM_MONITOR_RING_PFN,
                                  monitor_notification);
+            domain_unpause(d);
             break;
 
         case XEN_VM_EVENT_DISABLE:
             if ( ved->ring_page )
+            {
+                domain_pause(d);
                 rc = vm_event_disable(d, ved);
+                domain_unpause(d);
+            }
             break;
 
         case XEN_VM_EVENT_RESUME:
@@ -701,14 +713,20 @@ int vm_event_domctl(struct domain *d, 
xen_domctl_vm_event_op_t *vec,
             if ( !hap_enabled(d) )
                 break;
 
+            domain_pause(d);
             rc = vm_event_enable(d, vec, ved, _VPF_mem_sharing,
                                  HVM_PARAM_SHARING_RING_PFN,
                                  mem_sharing_notification);
+            domain_unpause(d);
             break;
 
         case XEN_VM_EVENT_DISABLE:
             if ( ved->ring_page )
+            {
+                domain_pause(d);
                 rc = vm_event_disable(d, ved);
+                domain_unpause(d);
+            }
             break;
 
         case XEN_VM_EVENT_RESUME:
-- 
1.9.1


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