x86/hvm: remove hvm_io_pending() check in hvmemul_do_io()

The check is done at the wrong point (since it is irrelevant if the
I/O is to be handled by the hypervisor) and its functionality can be
covered by returning X86EMUL_UNHANDLEABLE from hvm_send_assist_req()
instead.

This patch also removes the domain_crash() call from
hvm_send_assist_req(). Returning X86EMUL_UNHANDLEABLE allows the
higher layers of emulation to decide what to do instead.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>

xen/arch/x86/hvm/emulate.c

@@ -121,12 +121,6 @@ static int hvmemul_do_io(
         return X86EMUL_UNHANDLEABLE;
     }
 
-    if ( hvm_io_pending(curr) )
-    {
-        gdprintk(XENLOG_WARNING, "WARNING: io already pending?\n");
-        return X86EMUL_UNHANDLEABLE;
-    }
-
     vio->io_state = (data_is_addr || dir == IOREQ_WRITE) ?
         HVMIO_dispatched : HVMIO_awaiting_completion;
     vio->io_size = size;
@@ -188,8 +182,8 @@ static int hvmemul_do_io(
         }
         else
         {
-            rc = X86EMUL_RETRY;
-            if ( !hvm_send_assist_req(s, &p) )
+            rc = hvm_send_assist_req(s, &p);
+            if ( rc != X86EMUL_RETRY )
                 vio->io_state = HVMIO_none;
             else if ( data_is_addr || dir == IOREQ_WRITE )
                 rc = X86EMUL_OKAY;

xen/arch/x86/hvm/hvm.c

@@ -2605,7 +2605,7 @@ int hvm_buffered_io_send(ioreq_t *p)
     return 1;
 }
 
-bool_t hvm_send_assist_req(struct hvm_ioreq_server *s, ioreq_t *proto_p)
+int hvm_send_assist_req(struct hvm_ioreq_server *s, ioreq_t *proto_p)
 {
     struct vcpu *curr = current;
     struct domain *d = curr->domain;
@@ -2613,7 +2613,7 @@ bool_t hvm_send_assist_req(struct hvm_ioreq_server *s, ioreq_t *proto_p)
 
     ASSERT(s);
     if ( unlikely(!vcpu_start_shutdown_deferral(curr)) )
-        return 0; /* implicitly bins the i/o operation */
+        return X86EMUL_OKAY;
 
     list_for_each_entry ( sv,
                           &s->ioreq_vcpu_list,
@@ -2628,14 +2628,14 @@ bool_t hvm_send_assist_req(struct hvm_ioreq_server *s, ioreq_t *proto_p)
             {
                 gprintk(XENLOG_ERR, "device model set bad IO state %d\n",
                         p->state);
-                goto crash;
+                break;
             }
 
             if ( unlikely(p->vp_eport != port) )
             {
                 gprintk(XENLOG_ERR, "device model set bad event channel %d\n",
                         p->vp_eport);
-                goto crash;
+                break;
             }
 
             proto_p->state = STATE_IOREQ_NONE;
@@ -2651,15 +2651,11 @@ bool_t hvm_send_assist_req(struct hvm_ioreq_server *s, ioreq_t *proto_p)
              */
             p->state = STATE_IOREQ_READY;
             notify_via_xen_event_channel(d, port);
-            break;
+            return X86EMUL_RETRY;
         }
     }
 
-    return 1;
-
- crash:
-    domain_crash(d);
-    return 0;
+    return X86EMUL_UNHANDLEABLE;
 }
 
 void hvm_complete_assist_req(ioreq_t *p)

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

@@ -230,7 +230,7 @@ void hvm_vcpu_reset_state(struct vcpu *v, uint16_t cs, uint16_t ip);
 
 struct hvm_ioreq_server *hvm_select_ioreq_server(struct domain *d,
                                                  ioreq_t *p);
-bool_t hvm_send_assist_req(struct hvm_ioreq_server *s, ioreq_t *p);
+int hvm_send_assist_req(struct hvm_ioreq_server *s, ioreq_t *p);
 void hvm_broadcast_assist_req(ioreq_t *p);
 void hvm_complete_assist_req(ioreq_t *p);