1 files changed, 17 insertions, 14 deletions

diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
index d3d91dae065c..944eaeb8e0cf 100644
--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c
@@ -214,24 +214,24 @@ static int xen_hvm_console_init(void)
         /* already configured */
         if (info->intf != NULL)
                 return 0;
-
+        /*
+         * If the toolstack (or the hypervisor) hasn't set these values, the
+         * default value is 0. Even though mfn = 0 and evtchn = 0 are
+         * theoretically correct values, in practice they never are and they
+         * mean that a legacy toolstack hasn't initialized the pv console correctly.
+         */
         r = hvm_get_parameter(HVM_PARAM_CONSOLE_EVTCHN, &v);
-        if (r < 0) {
-                kfree(info);
-                return -ENODEV;
-        }
+        if (r < 0 || v == 0)
+                goto err;
         info->evtchn = v;
-        hvm_get_parameter(HVM_PARAM_CONSOLE_PFN, &v);
-        if (r < 0) {
-                kfree(info);
-                return -ENODEV;
-        }
+        v = 0;
+        r = hvm_get_parameter(HVM_PARAM_CONSOLE_PFN, &v);
+        if (r < 0 || v == 0)
+                goto err;
         mfn = v;
         info->intf = ioremap(mfn << PAGE_SHIFT, PAGE_SIZE);
-        if (info->intf == NULL) {
-                kfree(info);
-                return -ENODEV;
-        }
+        if (info->intf == NULL)
+                goto err;
         info->vtermno = HVC_COOKIE;
 
         spin_lock(&xencons_lock);
@@ -239,6 +239,9 @@ static int xen_hvm_console_init(void)
         spin_unlock(&xencons_lock);
 
         return 0;
+err:
+        kfree(info);
+        return -ENODEV;
 }
 
 static int xen_pv_console_init(void)