[PATCH v2 for-4.22? 5/7] domctl: correct return value of XEN_DOMCTL_[gs]etvcpuaffinity

[Jan Beulich <jbeulich@xxxxxxxx>]

cpumask_to_xenctl_bitmap() may return errors. Clearing the error indicator
of an earlier such call by a (successful) later call is misleading the
caller. For "set", keep setting soft affinity if the hard affinity copy-
back fails; only accumulate respective errors.

While fiddling with return values, also drop a redundant clearing of
"ret". This eliminates a Misra C:2012 rule 2.2 ("There shall be no dead
code") violation.

Fixes: 6e4ecc6d5884 ("sched: DOMCTL_*vcpuaffinity works with hard and soft 
affinity")
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Release-Acked-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
v2: Consistently return first error. Integrate into series.

--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -1708,7 +1708,7 @@ int vcpu_affinity_domctl(struct domain *
 {
     struct vcpu *v;
     const struct sched_unit *unit;
-    int ret = 0;
+    int ret = 0, hret = 0;
 
     if ( vcpuaff->vcpu >= d->max_vcpus )
         return -EINVAL;
@@ -1746,19 +1746,17 @@ int vcpu_affinity_domctl(struct domain *
         if ( vcpuaff->flags & XEN_VCPUAFFINITY_FORCE )
             vcpu_temporary_affinity(v, NR_CPUS, VCPU_AFFINITY_OVERRIDE);
 
-        ret = 0;
-
         /*
          * We both set a new affinity and report back to the caller what
          * the scheduler will be effectively using.
          */
         if ( vcpuaff->flags & XEN_VCPUAFFINITY_HARD )
         {
-            ret = xenctl_bitmap_to_bitmap(cpumask_bits(new_affinity),
-                                          &vcpuaff->cpumap_hard, nr_cpu_ids);
-            if ( !ret )
-                ret = vcpu_set_hard_affinity(v, new_affinity);
-            if ( ret )
+            hret = xenctl_bitmap_to_bitmap(cpumask_bits(new_affinity),
+                                           &vcpuaff->cpumap_hard, nr_cpu_ids);
+            if ( !hret )
+                hret = vcpu_set_hard_affinity(v, new_affinity);
+            if ( hret )
                 goto setvcpuaffinity_out;
 
             /*
@@ -1766,7 +1764,7 @@ int vcpu_affinity_domctl(struct domain *
              * cpupool's online mask and the new hard affinity.
              */
             cpumask_and(new_affinity, online, unit->cpu_hard_affinity);
-            ret = cpumask_to_xenctl_bitmap(&vcpuaff->cpumap_hard, 
new_affinity);
+            hret = cpumask_to_xenctl_bitmap(&vcpuaff->cpumap_hard, 
new_affinity);
         }
         if ( vcpuaff->flags & XEN_VCPUAFFINITY_SOFT )
         {
@@ -1804,14 +1802,14 @@ int vcpu_affinity_domctl(struct domain *
     else
     {
         if ( vcpuaff->flags & XEN_VCPUAFFINITY_HARD )
-            ret = cpumask_to_xenctl_bitmap(&vcpuaff->cpumap_hard,
-                                           unit->cpu_hard_affinity);
+            hret = cpumask_to_xenctl_bitmap(&vcpuaff->cpumap_hard,
+                                            unit->cpu_hard_affinity);
         if ( vcpuaff->flags & XEN_VCPUAFFINITY_SOFT )
             ret = cpumask_to_xenctl_bitmap(&vcpuaff->cpumap_soft,
                                            unit->cpu_soft_affinity);
     }
 
-    return ret;
+    return hret ?: ret;
 }
 
 bool alloc_affinity_masks(struct affinity_masks *affinity)