[PATCH V2] xen: Fix BUFIOREQ evtchn init for a stubdom.

[Anthony PERARD <anthony.perard@citrix.com>]

This is a missing part from the previous patch that add the BUFIOREQ_EVTCHN
parameter. This patch changes the ownership of the buifioreq event channel to
the stubdom (when HVM_PARAM_DM_DOMAIN is set within the stubdom).

This patch introduces an helper to replace a xen port.

This fix the initialization of QEMU inside the stubdomain.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
---
Change:
  - an helper
  - the replacement of the buferioreq evtchn is inside iorp->lock now.

 xen/arch/x86/hvm/hvm.c |   37 ++++++++++++++++++++++++++++---------
 1 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index e0d495d..e8e86c0 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3664,6 +3664,21 @@ static int hvmop_flush_tlb_all(void)
     return 0;
 }
 
+static int hvm_replace_event_channel(struct vcpu *v, uint64_t remote_domid,
+                                     int *port)
+{
+    int old_port, new_port;
+
+    new_port = alloc_unbound_xen_event_channel(v, remote_domid, NULL);
+    if ( new_port < 0 )
+        return new_port;
+
+    /* xchg() ensures that only we free_xen_event_channel() */
+    old_port = xchg(port, new_port);
+    free_xen_event_channel(v, old_port);
+    return 0;
+}
+
 long do_hvm_op(unsigned long op, XEN_GUEST_HANDLE(void) arg)
 
 {
@@ -3777,17 +3792,21 @@ long do_hvm_op(unsigned long op, XEN_GUEST_HANDLE(void) arg)
                 iorp = &d->arch.hvm_domain.ioreq;
                 for_each_vcpu ( d, v )
                 {
-                    int old_port, new_port;
-                    new_port = alloc_unbound_xen_event_channel(
-                        v, a.value, NULL);
-                    if ( new_port < 0 )
-                    {
-                        rc = new_port;
+                    rc = hvm_replace_event_channel(v, a.value,
+                                                   &v->arch.hvm_vcpu.xen_port);
+                    if ( rc )
                         break;
+
+                    if ( v->vcpu_id == 0 )
+                    {
+                        spin_lock(&iorp->lock);
+                        rc = hvm_replace_event_channel(v, a.value,
+                            (int*)&v->domain->arch.hvm_domain.params[HVM_PARAM_BUFIOREQ_EVTCHN]);
+                        spin_unlock(&iorp->lock);
+                        if ( rc )
+                            break;
                     }
-                    /* xchg() ensures that only we free_xen_event_channel() */
-                    old_port = xchg(&v->arch.hvm_vcpu.xen_port, new_port);
-                    free_xen_event_channel(v, old_port);
+
                     spin_lock(&iorp->lock);
                     if ( iorp->va != NULL )
                         get_ioreq(v)->vp_eport = v->arch.hvm_vcpu.xen_port;
-- 
Anthony PERARD