x86/hvm: stop passing explicit domid to hvm_create_ioreq_server()

Only in the legacy 'default server' case do we pass anything other than
current->domain->domain_id, and in that case we pass the value of
HVM_PARAM_DM_DOMAIN.

The only known user of HVM_PARAM_DM_DOMAIN is qemu-trad (and only when
compiled as a stubdom), which always sets it to DOMID_SELF (ignoring the
return value of xc_set_hvm_param) [1] and never reads it.

This patch:

- Disallows setting HVM_PARAM_DM_DOMAIN to anything other than DOMID_SELF
  and removes the call to hvm_set_dm_domain().
- Stops passing a domid to hvm_create_ioreq_server()
- Changes hvm_create_ioreq_server() to always set
  current->domain->domain_id as the domid of the emulating domain
- Removes the hvm_set_dm_domain() implementation since it is no longer
  needed.

[1] http://xenbits.xen.org/gitweb/?p=qemu-xen-traditional.git;a=blob;f=hw/xen_machine_fv.c;#l299

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

xen/arch/x86/hvm/dm.c

@@ -402,7 +402,6 @@ static int dm_op(const struct dmop_args *op_args)
     {
     case XEN_DMOP_create_ioreq_server:
     {
-        struct domain *curr_d = current->domain;
         struct xen_dm_op_create_ioreq_server *data =
             &op.u.create_ioreq_server;
 
@@ -412,8 +411,8 @@ static int dm_op(const struct dmop_args *op_args)
         if ( data->pad[0] || data->pad[1] || data->pad[2] )
             break;
 
-        rc = hvm_create_ioreq_server(d, curr_d->domain_id, false,
-                                     data->handle_bufioreq, &data->id);
+        rc = hvm_create_ioreq_server(d, false, data->handle_bufioreq,
+                                     &data->id);
         break;
     }
 

xen/arch/x86/hvm/hvm.c

@@ -4205,10 +4205,11 @@ static int hvmop_set_param(
         domctl_lock_release();
         break;
     case HVM_PARAM_DM_DOMAIN:
-        if ( a.value == DOMID_SELF )
-            a.value = curr_d->domain_id;
+        /* The only value this should ever be set to is DOMID_SELF */
+        if ( a.value != DOMID_SELF )
+            rc = -EINVAL;
 
-        rc = hvm_set_dm_domain(d, a.value);
+        a.value = curr_d->domain_id;
         break;
     case HVM_PARAM_ACPI_S_STATE:
         rc = 0;
@@ -4449,9 +4450,7 @@ static int hvmop_get_param(
          */
         if ( !d->creation_finished )
         {
-            domid_t domid = d->arch.hvm_domain.params[HVM_PARAM_DM_DOMAIN];
-
-            rc = hvm_create_ioreq_server(d, domid, true,
+            rc = hvm_create_ioreq_server(d, true,
                                          HVM_IOREQSRV_BUFIOREQ_LEGACY, NULL);
             if ( rc != 0 && rc != -EEXIST )
                 goto out;

xen/arch/x86/hvm/ioreq.c

@@ -599,16 +599,15 @@ static void hvm_ioreq_server_disable(struct hvm_ioreq_server *s,
 }
 
 static int hvm_ioreq_server_init(struct hvm_ioreq_server *s,
-                                 struct domain *d, domid_t domid,
-                                 bool is_default, int bufioreq_handling,
-                                 ioservid_t id)
+                                 struct domain *d, bool is_default,
+                                 int bufioreq_handling, ioservid_t id)
 {
     struct vcpu *v;
     int rc;
 
     s->id = id;
     s->domain = d;
-    s->domid = domid;
+    s->domid = current->domain->domain_id;
 
     spin_lock_init(&s->lock);
     INIT_LIST_HEAD(&s->ioreq_vcpu_list);
@@ -680,9 +679,8 @@ static ioservid_t next_ioservid(struct domain *d)
     return id;
 }
 
-int hvm_create_ioreq_server(struct domain *d, domid_t domid,
-                            bool is_default, int bufioreq_handling,
-                            ioservid_t *id)
+int hvm_create_ioreq_server(struct domain *d, bool is_default,
+                            int bufioreq_handling, ioservid_t *id)
 {
     struct hvm_ioreq_server *s;
     int rc;
@@ -702,7 +700,7 @@ int hvm_create_ioreq_server(struct domain *d, domid_t domid,
     if ( is_default && d->arch.hvm_domain.default_ioreq_server != NULL )
         goto fail2;
 
-    rc = hvm_ioreq_server_init(s, d, domid, is_default, bufioreq_handling,
+    rc = hvm_ioreq_server_init(s, d, is_default, bufioreq_handling,
                                next_ioservid(d));
     if ( rc )
         goto fail3;
@@ -1089,80 +1087,6 @@ void hvm_destroy_all_ioreq_servers(struct domain *d)
     spin_unlock_recursive(&d->arch.hvm_domain.ioreq_server.lock);
 }
 
-static int hvm_replace_event_channel(struct vcpu *v, domid_t remote_domid,
-                                     evtchn_port_t *p_port)
-{
-    int old_port, new_port;
-
-    new_port = alloc_unbound_xen_event_channel(v->domain, v->vcpu_id,
-                                               remote_domid, NULL);
-    if ( new_port < 0 )
-        return new_port;
-
-    /* xchg() ensures that only we call free_xen_event_channel(). */
-    old_port = xchg(p_port, new_port);
-    free_xen_event_channel(v->domain, old_port);
-    return 0;
-}
-
-int hvm_set_dm_domain(struct domain *d, domid_t domid)
-{
-    struct hvm_ioreq_server *s;
-    int rc = 0;
-
-    spin_lock_recursive(&d->arch.hvm_domain.ioreq_server.lock);
-
-    /*
-     * Lack of ioreq server is not a failure. HVM_PARAM_DM_DOMAIN will
-     * still be set and thus, when the server is created, it will have
-     * the correct domid.
-     */
-    s = d->arch.hvm_domain.default_ioreq_server;
-    if ( !s )
-        goto done;
-
-    domain_pause(d);
-    spin_lock(&s->lock);
-
-    if ( s->domid != domid )
-    {
-        struct hvm_ioreq_vcpu *sv;
-
-        list_for_each_entry ( sv,
-                              &s->ioreq_vcpu_list,
-                              list_entry )
-        {
-            struct vcpu *v = sv->vcpu;
-
-            if ( v->vcpu_id == 0 )
-            {
-                rc = hvm_replace_event_channel(v, domid,
-                                               &s->bufioreq_evtchn);
-                if ( rc )
-                    break;
-
-                d->arch.hvm_domain.params[HVM_PARAM_BUFIOREQ_EVTCHN] =
-                    s->bufioreq_evtchn;
-            }
-
-            rc = hvm_replace_event_channel(v, domid, &sv->ioreq_evtchn);
-            if ( rc )
-                break;
-
-            hvm_update_ioreq_evtchn(s, sv);
-        }
-
-        s->domid = domid;
-    }
-
-    spin_unlock(&s->lock);
-    domain_unpause(d);
-
- done:
-    spin_unlock_recursive(&d->arch.hvm_domain.ioreq_server.lock);
-    return rc;
-}
-
 struct hvm_ioreq_server *hvm_select_ioreq_server(struct domain *d,
                                                  ioreq_t *p)
 {

xen/include/asm-x86/hvm/ioreq.h

@@ -23,9 +23,8 @@ bool hvm_io_pending(struct vcpu *v);
 bool handle_hvm_io_completion(struct vcpu *v);
 bool is_ioreq_server_page(struct domain *d, const struct page_info *page);
 
-int hvm_create_ioreq_server(struct domain *d, domid_t domid,
-                            bool is_default, int bufioreq_handling,
-                            ioservid_t *id);
+int hvm_create_ioreq_server(struct domain *d, bool is_default,
+                            int bufioreq_handling, ioservid_t *id);
 int hvm_destroy_ioreq_server(struct domain *d, ioservid_t id);
 int hvm_get_ioreq_server_info(struct domain *d, ioservid_t id,
                               unsigned long *ioreq_gfn,
@@ -46,8 +45,6 @@ int hvm_all_ioreq_servers_add_vcpu(struct domain *d, struct vcpu *v);
 void hvm_all_ioreq_servers_remove_vcpu(struct domain *d, struct vcpu *v);
 void hvm_destroy_all_ioreq_servers(struct domain *d);
 
-int hvm_set_dm_domain(struct domain *d, domid_t domid);
-
 struct hvm_ioreq_server *hvm_select_ioreq_server(struct domain *d,
                                                  ioreq_t *p);
 int hvm_send_ioreq(struct hvm_ioreq_server *s, ioreq_t *proto_p,