[Xen-devel] [PATCH 2/2] xenbus: don't rely on xen_initial_domain to detect local xenstore

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxxx>
Reviewed-by: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
---
 drivers/xen/xenbus/xenbus_probe.c |  101 +++++++++++++++++++-----------------
 1 files changed, 53 insertions(+), 48 deletions(-)

diff --git a/drivers/xen/xenbus/xenbus_probe.c 
b/drivers/xen/xenbus/xenbus_probe.c
index 82bf38c..cef9b0b 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -684,64 +684,74 @@ 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. */
@@ -760,12 +770,7 @@ 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;
 }
 
-- 
1.7.6.4


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