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.
 */
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/resource.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_barebones();

	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);
	/*
	 * Number of file descriptors reqired, KVM_CAP_MAX_VCPUS for vCPU fds +
	 * an arbitrary number for everything else.
	 */
	int nr_fds_wanted = kvm_max_vcpus + 100;
	struct rlimit rl;

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

	/*
	 * Check that we're allowed to open nr_fds_wanted file descriptors and
	 * try raising the limits if needed.
	 */
	TEST_ASSERT(!getrlimit(RLIMIT_NOFILE, &rl), "getrlimit() failed!");

	if (rl.rlim_cur < nr_fds_wanted) {
		rl.rlim_cur = nr_fds_wanted;
		if (rl.rlim_max < nr_fds_wanted) {
			int old_rlim_max = rl.rlim_max;
			rl.rlim_max = nr_fds_wanted;

			int r = setrlimit(RLIMIT_NOFILE, &rl);
			__TEST_REQUIRE(r >= 0,
				       "RLIMIT_NOFILE hard limit is too low (%d, wanted %d)",
				       old_rlim_max, nr_fds_wanted);
		} else {
			TEST_ASSERT(!setrlimit(RLIMIT_NOFILE, &rl), "setrlimit() failed!");
		}
	}

	/*
	 * 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_IDS (%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;
}