KVM: use modern cpumask primitives, no cpumask_t on stack
We're getting rid on on-stack cpumasks for large NR_CPUS.
1) Use cpumask_var_t/alloc_cpumask_var.
2) smp_call_function_mask -> smp_call_function_many
3) cpus_clear, cpus_empty, cpu_set -> cpumask_clear, cpumask_empty,
cpumask_set_cpu.
This actually generates slightly smaller code than the old one with
CONFIG_CPUMASKS_OFFSTACK=n. (gcc knows that cpus cannot be NULL in
that case, where cpumask_var_t is cpumask_t[1]).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index ba4275d..2d6ca79 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -555,12 +555,14 @@
static bool make_all_cpus_request(struct kvm *kvm, unsigned int req)
{
int i, cpu, me;
- cpumask_t cpus;
- bool called = false;
+ cpumask_var_t cpus;
+ bool called = true;
struct kvm_vcpu *vcpu;
+ if (alloc_cpumask_var(&cpus, GFP_ATOMIC))
+ cpumask_clear(cpus);
+
me = get_cpu();
- cpus_clear(cpus);
for (i = 0; i < KVM_MAX_VCPUS; ++i) {
vcpu = kvm->vcpus[i];
if (!vcpu)
@@ -568,14 +570,17 @@
if (test_and_set_bit(req, &vcpu->requests))
continue;
cpu = vcpu->cpu;
- if (cpu != -1 && cpu != me)
- cpu_set(cpu, cpus);
+ if (cpus != NULL && cpu != -1 && cpu != me)
+ cpumask_set_cpu(cpu, cpus);
}
- if (!cpus_empty(cpus)) {
- smp_call_function_mask(cpus, ack_flush, NULL, 1);
- called = true;
- }
+ if (unlikely(cpus == NULL))
+ smp_call_function_many(cpu_online_mask, ack_flush, NULL, 1);
+ else if (!cpumask_empty(cpus))
+ smp_call_function_many(cpus, ack_flush, NULL, 1);
+ else
+ called = false;
put_cpu();
+ free_cpumask_var(cpus);
return called;
}