xenbus: don't rely on xen_initial_domain to detect local xenstore

The xenstore daemon does not have to run in the xen initial domain;
however, Linux currently uses xen_initial_domain to test if a loopback
event channel should be used instead of the event channel provided in
Xen's start_info structure. Instead, if the event channel passed in the
start_info structure is not valid, assume that this domain will run
xenstored locally and set up the event channel.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Reviewed-by: Ian Campbell <Ian.Campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 53 insertions, 48 deletions

diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index d5347fe15882..13b0f05bafb7 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -696,64 +696,74 @@ static int __init xenbus_probe_initcall(void)
 
 device_initcall(xenbus_probe_initcall);
 
-static int __init xenbus_init(void)
+/* Set up event channel for xenstored which is run as a local process
+ * (this is normally used only in dom0)
+ */
+static int __init xenstored_local_init(void)
 {
         int err = 0;
         unsigned long page = 0;
+        struct evtchn_alloc_unbound alloc_unbound;
 
-        DPRINTK("");
+        /* Allocate Xenstore page */
+        page = get_zeroed_page(GFP_KERNEL);
+        if (!page)
+                goto out_err;
 
-        err = -ENODEV;
-        if (!xen_domain())
-                return err;
+        xen_store_mfn = xen_start_info->store_mfn =
+                pfn_to_mfn(virt_to_phys((void *)page) >>
+                           PAGE_SHIFT);
 
-        /*
-         * Domain0 doesn't have a store_evtchn or store_mfn yet.
-         */
-        if (xen_initial_domain()) {
-                struct evtchn_alloc_unbound alloc_unbound;
+        /* Next allocate a local port which xenstored can bind to */
+        alloc_unbound.dom        = DOMID_SELF;
+        alloc_unbound.remote_dom = DOMID_SELF;
 
-                /* Allocate Xenstore page */
-                page = get_zeroed_page(GFP_KERNEL);
-                if (!page)
-                        goto out_error;
+        err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
+                                          &alloc_unbound);
+        if (err == -ENOSYS)
+                goto out_err;
 
-                xen_store_mfn = xen_start_info->store_mfn =
-                        pfn_to_mfn(virt_to_phys((void *)page) >>
-                                   PAGE_SHIFT);
+        BUG_ON(err);
+        xen_store_evtchn = xen_start_info->store_evtchn =
+                alloc_unbound.port;
 
-                /* Next allocate a local port which xenstored can bind to */
-                alloc_unbound.dom        = DOMID_SELF;
-                alloc_unbound.remote_dom = DOMID_SELF;
+        return 0;
 
-                err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
-                                                  &alloc_unbound);
-                if (err == -ENOSYS)
-                        goto out_error;
+ out_err:
+        if (page != 0)
+                free_page(page);
+        return err;
+}
 
-                BUG_ON(err);
-                xen_store_evtchn = xen_start_info->store_evtchn =
-                        alloc_unbound.port;
+static int __init xenbus_init(void)
+{
+        int err = 0;
 
-                xen_store_interface = mfn_to_virt(xen_store_mfn);
+        if (!xen_domain())
+                return -ENODEV;
+
+        if (xen_hvm_domain()) {
+                uint64_t v = 0;
+                err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
+                if (err)
+                        goto out_error;
+                xen_store_evtchn = (int)v;
+                err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
+                if (err)
+                        goto out_error;
+                xen_store_mfn = (unsigned long)v;
+                xen_store_interface = ioremap(xen_store_mfn << PAGE_SHIFT, PAGE_SIZE);
         } else {
-                if (xen_hvm_domain()) {
-                        uint64_t v = 0;
-                        err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
-                        if (err)
-                                goto out_error;
-                        xen_store_evtchn = (int)v;
-                        err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
+                xen_store_evtchn = xen_start_info->store_evtchn;
+                xen_store_mfn = xen_start_info->store_mfn;
+                if (xen_store_evtchn)
+                        xenstored_ready = 1;
+                else {
+                        err = xenstored_local_init();
                         if (err)
                                 goto out_error;
-                        xen_store_mfn = (unsigned long)v;
-                        xen_store_interface = ioremap(xen_store_mfn << PAGE_SHIFT, PAGE_SIZE);
-                } else {
-                        xen_store_evtchn = xen_start_info->store_evtchn;
-                        xen_store_mfn = xen_start_info->store_mfn;
-                        xen_store_interface = mfn_to_virt(xen_store_mfn);
-                        xenstored_ready = 1;
                 }
+                xen_store_interface = mfn_to_virt(xen_store_mfn);
         }
 
         /* Initialize the interface to xenstore. */
@@ -772,12 +782,7 @@ static int __init xenbus_init(void)
         proc_mkdir("xen", NULL);
 #endif
 
-        return 0;
-
-  out_error:
-        if (page != 0)
-                free_page(page);
-
+ out_error:
         return err;
 }