[PATCH 2/3] x86/sysctl: Clean up XEN_SYSCTL_cpu_hotplug

[Andrew Cooper <andrew.cooper3@citrix.com>]

A future change is going to introduce two more cases.  Instead of opcoding the
XSM checks and contine_hypercall logic, collect the data into local variables.

Switch the default return value to -EOPNOTSUPP to distinguish a bad op from a
bad cpu index.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
---
 xen/arch/x86/sysctl.c | 30 +++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/xen/arch/x86/sysctl.c b/xen/arch/x86/sysctl.c
index 1916a3d..b3cc4b5 100644
--- a/xen/arch/x86/sysctl.c
+++ b/xen/arch/x86/sysctl.c
@@ -137,27 +137,35 @@ long arch_do_sysctl(
     case XEN_SYSCTL_cpu_hotplug:
     {
         unsigned int cpu = sysctl->u.cpu_hotplug.cpu;
+        bool plug;
+        long (*fn)(void *) = NULL;
+        void *hcpu = NULL;
 
         switch ( sysctl->u.cpu_hotplug.op )
         {
         case XEN_SYSCTL_CPU_HOTPLUG_ONLINE:
-            ret = xsm_resource_plug_core(XSM_HOOK);
-            if ( ret )
-                break;
-            ret = continue_hypercall_on_cpu(
-                0, cpu_up_helper, (void *)(unsigned long)cpu);
+            plug = true;
+            fn = cpu_up_helper;
+            hcpu = (void *)(unsigned long)cpu;
             break;
+
         case XEN_SYSCTL_CPU_HOTPLUG_OFFLINE:
-            ret = xsm_resource_unplug_core(XSM_HOOK);
-            if ( ret )
-                break;
-            ret = continue_hypercall_on_cpu(
-                0, cpu_down_helper, (void *)(unsigned long)cpu);
+            plug = false;
+            fn = cpu_down_helper;
+            hcpu = (void *)(unsigned long)cpu;
             break;
+
         default:
-            ret = -EINVAL;
+            ret = -EOPNOTSUPP;
             break;
         }
+
+        if ( !ret )
+            ret = plug ? xsm_resource_plug_core(XSM_HOOK)
+                       : xsm_resource_unplug_core(XSM_HOOK);
+
+        if ( !ret )
+            ret = continue_hypercall_on_cpu(0, fn, hcpu);
     }
     break;
 
-- 
2.1.4


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