[PATCH v2] xenbus: Allow PVH dom0 a non-local xenstore

[Jason Andryuk <jason.andryuk@xxxxxxx>]

Make xenbus_init() allow a non-local xenstore for a PVH dom0 - it is
currently forced to XS_LOCAL.  With Hyperlaunch booting dom0 and a
xenstore stubdom, dom0 can be handled as a regular XS_HVM following the
late init path.

Ideally we'd drop the use of xen_initial_domain() and just check for the
event channel instead.  However, ARM has a xen,enhanced no-xenstore
mode, where the event channel and PFN would both be 0.  Retain the
xen_initial_domain() check, and use that for an additional check when
the event channel is 0.

Check the full 64bit HVM_PARAM_STORE_EVTCHN value to catch the off
chance that high bits are set for the 32bit event channel.

Signed-off-by: Jason Andryuk <jason.andryuk@xxxxxxx>
Change-Id: I5506da42e4c6b8e85079fefb2f193c8de17c7437
---
v2:
Re-add xen_initial_domain() check to avoid breaking ARM's xen,enhanced
no-xenstore mode where event channel and PFN are both 0.

 drivers/xen/xenbus/xenbus_probe.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/xen/xenbus/xenbus_probe.c 
b/drivers/xen/xenbus/xenbus_probe.c
index 22d3f90ee205..b12cbd9663e3 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -969,9 +969,15 @@ static int __init xenbus_init(void)
        if (xen_pv_domain())
                xen_store_domain_type = XS_PV;
        if (xen_hvm_domain())
+       {
                xen_store_domain_type = XS_HVM;
-       if (xen_hvm_domain() && xen_initial_domain())
-               xen_store_domain_type = XS_LOCAL;
+               err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
+               if (err)
+                       goto out_error;
+               xen_store_evtchn = (int)v;
+               if (!v && xen_initial_domain())
+                       xen_store_domain_type = XS_LOCAL;
+       }
        if (xen_pv_domain() && !xen_start_info->store_evtchn)
                xen_store_domain_type = XS_LOCAL;
        if (xen_pv_domain() && xen_start_info->store_evtchn)
@@ -990,10 +996,6 @@ static int __init xenbus_init(void)
                xen_store_interface = gfn_to_virt(xen_store_gfn);
                break;
        case XS_HVM:
-               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;
-- 
2.34.1