constify vcpu_set_affinity()'s second parameter

None of the callers actually make use of the function's returning of
the old affinity through its second parameter, and eliminating this
capability allows some callers to no longer use a local variable here,
reducing their stack footprint significantly when building with large
NR_CPUS.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>

4 files changed, 6 insertions, 17 deletions

diff --git a/xen/arch/x86/cpu/mcheck/vmce.c b/xen/arch/x86/cpu/mcheck/vmce.c
index 0b8f4ba400..d764d57d20 100644
--- a/xen/arch/x86/cpu/mcheck/vmce.c
+++ b/xen/arch/x86/cpu/mcheck/vmce.c
@@ -304,7 +304,6 @@ int vmce_wrmsr(u32 msr, u64 val)
 int inject_vmce(struct domain *d)
 {
     int cpu = smp_processor_id();
-    cpumask_t affinity;
 
     /* PV guest and HVM guest have different vMCE# injection methods. */
     if ( !test_and_set_bool(d->vcpu[0]->mce_pending) )
@@ -323,11 +322,9 @@ int inject_vmce(struct domain *d)
             {
                 cpumask_copy(d->vcpu[0]->cpu_affinity_tmp,
                              d->vcpu[0]->cpu_affinity);
-                cpus_clear(affinity);
-                cpu_set(cpu, affinity);
                 mce_printk(MCE_VERBOSE, "MCE: CPU%d set affinity, old %d\n",
                            cpu, d->vcpu[0]->processor);
-                vcpu_set_affinity(d->vcpu[0], &affinity);
+                vcpu_set_affinity(d->vcpu[0], cpumask_of(cpu));
                 vcpu_kick(d->vcpu[0]);
             }
             else
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 0203613b53..e22e6d86fc 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -3113,7 +3113,6 @@ static void nmi_mce_softirq(void)
 {
     int cpu = smp_processor_id();
     struct softirq_trap *st = &per_cpu(softirq_trap, cpu);
-    cpumask_t affinity;
 
     BUG_ON(st == NULL);
     BUG_ON(st->vcpu == NULL);
@@ -3129,9 +3128,7 @@ static void nmi_mce_softirq(void)
          * Make sure to wakeup the vcpu on the
          * specified processor.
          */
-        cpus_clear(affinity);
-        cpu_set(st->processor, affinity);
-        vcpu_set_affinity(st->vcpu, &affinity);
+        vcpu_set_affinity(st->vcpu, cpumask_of(st->processor));
 
         /* Affinity is restored in the iret hypercall. */
     }
@@ -3201,14 +3198,11 @@ void async_exception_cleanup(struct vcpu *curr)
                  !test_and_set_bool(curr->mce_pending) )
             {
                 int cpu = smp_processor_id();
-                cpumask_t affinity;
 
                 cpumask_copy(curr->cpu_affinity_tmp, curr->cpu_affinity);
-                cpus_clear(affinity);
-                cpu_set(cpu, affinity);
                 printk(XENLOG_DEBUG "MCE: CPU%d set affinity, old %d\n",
                        cpu, curr->processor);
-                vcpu_set_affinity(curr, &affinity);
+                vcpu_set_affinity(curr, cpumask_of(cpu));
             }
         }
     }
diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index 105961ed5b..e909eec39d 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -587,9 +587,9 @@ int cpu_disable_scheduler(unsigned int cpu)
     return ret;
 }
 
-int vcpu_set_affinity(struct vcpu *v, cpumask_t *affinity)
+int vcpu_set_affinity(struct vcpu *v, const cpumask_t *affinity)
 {
-    cpumask_t online_affinity, old_affinity;
+    cpumask_t online_affinity;
     cpumask_t *online;
 
     if ( v->domain->is_pinned )
@@ -601,9 +601,7 @@ int vcpu_set_affinity(struct vcpu *v, cpumask_t *affinity)
 
     vcpu_schedule_lock_irq(v);
 
-    cpumask_copy(&old_affinity, v->cpu_affinity);
     cpumask_copy(v->cpu_affinity, affinity);
-    cpumask_copy(affinity, &old_affinity);
     if ( !cpumask_test_cpu(v->processor, v->cpu_affinity) )
         set_bit(_VPF_migrating, &v->pause_flags);
 
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 784bcecdab..4b9dc56cfe 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -617,7 +617,7 @@ void scheduler_free(struct scheduler *sched);
 int schedule_cpu_switch(unsigned int cpu, struct cpupool *c);
 void vcpu_force_reschedule(struct vcpu *v);
 int cpu_disable_scheduler(unsigned int cpu);
-int vcpu_set_affinity(struct vcpu *v, cpumask_t *affinity);
+int vcpu_set_affinity(struct vcpu *v, const cpumask_t *affinity);
 
 void vcpu_runstate_get(struct vcpu *v, struct vcpu_runstate_info *runstate);
 uint64_t get_cpu_idle_time(unsigned int cpu);