linux/tools/testing/selftests/kvm/kvm_create_max_vcpus.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * kvm_create_max_vcpus
 *
 * Copyright (C) 2019, Google LLC.
 *
 * Test for KVM_CAP_MAX_VCPUS and KVM_CAP_MAX_VCPU_ID.
 */

#define _GNU_SOURCE /* for program_invocation_short_name */
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "test_util.h"

#include "kvm_util.h"
#include "asm/kvm.h"
#include "linux/kvm.h"

void test_vcpu_creation(int first_vcpu_id, int num_vcpus)
{
	struct kvm_vm *vm;
	int i;

	pr_info("Testing creating %d vCPUs, with IDs %d...%d.\n",
		num_vcpus, first_vcpu_id, first_vcpu_id + num_vcpus - 1);

	vm = vm_create(VM_MODE_DEFAULT, DEFAULT_GUEST_PHY_PAGES, O_RDWR);

	for (i = first_vcpu_id; i < first_vcpu_id + num_vcpus; i++)
		/* This asserts that the vCPU was created. */
		vm_vcpu_add(vm, i);

	kvm_vm_free(vm);
}

int main(int argc, char *argv[])
{
	int kvm_max_vcpu_id = kvm_check_cap(KVM_CAP_MAX_VCPU_ID);
	int kvm_max_vcpus = kvm_check_cap(KVM_CAP_MAX_VCPUS);

	pr_info("KVM_CAP_MAX_VCPU_ID: %d\n", kvm_max_vcpu_id);
	pr_info("KVM_CAP_MAX_VCPUS: %d\n", kvm_max_vcpus);

	/*
	 * Upstream KVM prior to 4.8 does not support KVM_CAP_MAX_VCPU_ID.
	 * Userspace is supposed to use KVM_CAP_MAX_VCPUS as the maximum ID
	 * in this case.
	 */
	if (!kvm_max_vcpu_id)
		kvm_max_vcpu_id = kvm_max_vcpus;

	TEST_ASSERT(kvm_max_vcpu_id >= kvm_max_vcpus,
		    "KVM_MAX_VCPU_ID (%d) must be at least as large as KVM_MAX_VCPUS (%d).",
		    kvm_max_vcpu_id, kvm_max_vcpus);

	test_vcpu_creation(0, kvm_max_vcpus);

	if (kvm_max_vcpu_id > kvm_max_vcpus)
		test_vcpu_creation(
			kvm_max_vcpu_id - kvm_max_vcpus, kvm_max_vcpus);

	return 0;
}