KVM: use modern cpumask primitives, no cpumask_t on stack (6ef7a1bc) · Commits · 戴 / test

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>

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;
		}

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