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Commit 6ef7a1bc authored by Rusty Russell's avatar Rusty Russell Committed by Avi Kivity
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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: default avatarRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 49846896

virt/kvm/kvm_main.c

+14 −9
Original line number Diff line number Diff line
@@ -555,12 +555,14 @@ static void ack_flush(void *_completed) 
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 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req) 
		if (test_and_set_bit(req, &vcpu->requests))

			continue;

		cpu = vcpu->cpu;

		if (cpu != -1 && cpu != me)

			cpu_set(cpu, cpus);

	}

	if (!cpus_empty(cpus)) {

		smp_call_function_mask(cpus, ack_flush, NULL, 1);

		called = true;

		if (cpus != NULL && cpu != -1 && cpu != me)

			cpumask_set_cpu(cpu, cpus);

	}

	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;

}