[Xen-changelog] [xen master] vm_event: synchronize vCPU state in vm_event_resume()

[patchbot@xxxxxxx]

commit cbfe4db8d750f3efdd11d482934b1cbfbe4284e6
Author:     Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
AuthorDate: Fri Aug 12 16:51:36 2016 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Aug 12 16:51:36 2016 +0200

    vm_event: synchronize vCPU state in vm_event_resume()
    
    Vm_event_vcpu_pause() needs to use vcpu_pause_nosync() in order
    for the current vCPU to not get stuck. A consequence of this is
    that the custom vm_event response handlers will not always see
    the real vCPU state in v->arch.user_regs. This patch makes sure
    that the state is always synchronized in vm_event_resume, before
    any handlers have been called. This problem especially affects
    vm_event_set_registers().
    
    Simply checking vm_event_pause_count to make sure the vCPU is
    paused suffices since there's only one ring / consumer at a
    time, and events are being processed one-by-one, so the
    toolstack won't unpause the vCPU behind our backs.
    
    Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
    Acked-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
---
 xen/common/vm_event.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/xen/common/vm_event.c b/xen/common/vm_event.c
index e2111c5..8398af7 100644
--- a/xen/common/vm_event.c
+++ b/xen/common/vm_event.c
@@ -388,6 +388,13 @@ void vm_event_resume(struct domain *d, struct 
vm_event_domain *ved)
         v = d->vcpu[rsp.vcpu_id];
 
         /*
+         * Make sure the vCPU state has been synchronized for the custom
+         * handlers.
+         */
+        if ( atomic_read(&v->vm_event_pause_count) )
+            sync_vcpu_execstate(v);
+
+        /*
          * In some cases the response type needs extra handling, so here
          * we call the appropriate handlers.
          */
--
generated by git-patchbot for /home/xen/git/xen.git#master

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