Commit 61f6fadb authored by Raghavendra Rao Ananta's avatar Raghavendra Rao Ananta Committed by Marc Zyngier
Browse files

KVM: arm64: selftests: arch_timer: Support vCPU migration 



Since the timer stack (hardware and KVM) is per-CPU, there
are potential chances for races to occur when the scheduler
decides to migrate a vCPU thread to a different physical CPU.
Hence, include an option to stress-test this part as well by
forcing the vCPUs to migrate across physical CPUs in the
system at a particular rate.

Originally, the bug for the fix with commit 3134cc8b
("KVM: arm64: vgic: Resample HW pending state on deactivation")
was discovered using arch_timer test with vCPU migrations and
can be easily reproduced.

Signed-off-by: default avatarRaghavendra Rao Ananta <rananta@google.com>
Reviewed-by: default avatarAndrew Jones <drjones@redhat.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211007233439.1826892-16-rananta@google.com
parent 4959d865

tools/testing/selftests/kvm/aarch64/arch_timer.c

+114 −1
Original line number Diff line number Diff line
@@ -14,6 +14,8 @@ 
 *

 * The test provides command-line options to configure the timer's

 * period (-p), number of vCPUs (-n), and iterations per stage (-i).

 * To stress-test the timer stack even more, an option to migrate the

 * vCPUs across pCPUs (-m), at a particular rate, is also provided.

 *

 * Copyright (c) 2021, Google LLC.

 */
@@ -24,6 +26,8 @@ 
#include <pthread.h>

#include <linux/kvm.h>

#include <linux/sizes.h>

#include <linux/bitmap.h>

#include <sys/sysinfo.h>



#include "kvm_util.h"

#include "processor.h"
@@ -36,17 +40,20 @@ 
#define NR_TEST_ITERS_DEF		5

#define TIMER_TEST_PERIOD_MS_DEF	10

#define TIMER_TEST_ERR_MARGIN_US	100

#define TIMER_TEST_MIGRATION_FREQ_MS	2



struct test_args {

	int nr_vcpus;

	int nr_iter;

	int timer_period_ms;

	int migration_freq_ms;

};



static struct test_args test_args = {

	.nr_vcpus = NR_VCPUS_DEF,

	.nr_iter = NR_TEST_ITERS_DEF,

	.timer_period_ms = TIMER_TEST_PERIOD_MS_DEF,

	.migration_freq_ms = TIMER_TEST_MIGRATION_FREQ_MS,

};



#define msecs_to_usecs(msec)		((msec) * 1000LL)
@@ -80,6 +87,9 @@ static struct test_vcpu_shared_data vcpu_shared_data[KVM_MAX_VCPUS]; 


static int vtimer_irq, ptimer_irq;



static unsigned long *vcpu_done_map;

static pthread_mutex_t vcpu_done_map_lock;



static void

guest_configure_timer_action(struct test_vcpu_shared_data *shared_data)

{
@@ -215,6 +225,11 @@ static void *test_vcpu_run(void *arg) 


	vcpu_run(vm, vcpuid);



	/* Currently, any exit from guest is an indication of completion */

	pthread_mutex_lock(&vcpu_done_map_lock);

	set_bit(vcpuid, vcpu_done_map);

	pthread_mutex_unlock(&vcpu_done_map_lock);



	switch (get_ucall(vm, vcpuid, &uc)) {

	case UCALL_SYNC:

	case UCALL_DONE:
@@ -233,9 +248,78 @@ static void *test_vcpu_run(void *arg) 
	return NULL;

}



static uint32_t test_get_pcpu(void)

{

	uint32_t pcpu;

	unsigned int nproc_conf;

	cpu_set_t online_cpuset;



	nproc_conf = get_nprocs_conf();

	sched_getaffinity(0, sizeof(cpu_set_t), &online_cpuset);



	/* Randomly find an available pCPU to place a vCPU on */

	do {

		pcpu = rand() % nproc_conf;

	} while (!CPU_ISSET(pcpu, &online_cpuset));



	return pcpu;

}



static int test_migrate_vcpu(struct test_vcpu *vcpu)

{

	int ret;

	cpu_set_t cpuset;

	uint32_t new_pcpu = test_get_pcpu();



	CPU_ZERO(&cpuset);

	CPU_SET(new_pcpu, &cpuset);



	pr_debug("Migrating vCPU: %u to pCPU: %u\n", vcpu->vcpuid, new_pcpu);



	ret = pthread_setaffinity_np(vcpu->pt_vcpu_run,

					sizeof(cpuset), &cpuset);



	/* Allow the error where the vCPU thread is already finished */

	TEST_ASSERT(ret == 0 || ret == ESRCH,

			"Failed to migrate the vCPU:%u to pCPU: %u; ret: %d\n",

			vcpu->vcpuid, new_pcpu, ret);



	return ret;

}



static void *test_vcpu_migration(void *arg)

{

	unsigned int i, n_done;

	bool vcpu_done;



	do {

		usleep(msecs_to_usecs(test_args.migration_freq_ms));



		for (n_done = 0, i = 0; i < test_args.nr_vcpus; i++) {

			pthread_mutex_lock(&vcpu_done_map_lock);

			vcpu_done = test_bit(i, vcpu_done_map);

			pthread_mutex_unlock(&vcpu_done_map_lock);



			if (vcpu_done) {

				n_done++;

				continue;

			}



			test_migrate_vcpu(&test_vcpu[i]);

		}

	} while (test_args.nr_vcpus != n_done);



	return NULL;

}



static void test_run(struct kvm_vm *vm)

{

	int i, ret;

	pthread_t pt_vcpu_migration;



	pthread_mutex_init(&vcpu_done_map_lock, NULL);

	vcpu_done_map = bitmap_zalloc(test_args.nr_vcpus);

	TEST_ASSERT(vcpu_done_map, "Failed to allocate vcpu done bitmap\n");



	for (i = 0; i < test_args.nr_vcpus; i++) {

		ret = pthread_create(&test_vcpu[i].pt_vcpu_run, NULL,
@@ -243,8 +327,23 @@ static void test_run(struct kvm_vm *vm) 
		TEST_ASSERT(!ret, "Failed to create vCPU-%d pthread\n", i);

	}



	/* Spawn a thread to control the vCPU migrations */

	if (test_args.migration_freq_ms) {

		srand(time(NULL));



		ret = pthread_create(&pt_vcpu_migration, NULL,

					test_vcpu_migration, NULL);

		TEST_ASSERT(!ret, "Failed to create the migration pthread\n");

	}





	for (i = 0; i < test_args.nr_vcpus; i++)

		pthread_join(test_vcpu[i].pt_vcpu_run, NULL);



	if (test_args.migration_freq_ms)

		pthread_join(pt_vcpu_migration, NULL);



	bitmap_free(vcpu_done_map);

}



static void test_init_timer_irq(struct kvm_vm *vm)
@@ -301,6 +400,8 @@ static void test_print_help(char *name) 
		NR_TEST_ITERS_DEF);

	pr_info("\t-p: Periodicity (in ms) of the guest timer (default: %u)\n",

		TIMER_TEST_PERIOD_MS_DEF);

	pr_info("\t-m: Frequency (in ms) of vCPUs to migrate to different pCPU. 0 to turn off (default: %u)\n",

		TIMER_TEST_MIGRATION_FREQ_MS);

	pr_info("\t-h: print this help screen\n");

}
@@ -308,7 +409,7 @@ static bool parse_args(int argc, char *argv[]) 
{

	int opt;



	while ((opt = getopt(argc, argv, "hn:i:p:")) != -1) {

	while ((opt = getopt(argc, argv, "hn:i:p:m:")) != -1) {

		switch (opt) {

		case 'n':

			test_args.nr_vcpus = atoi(optarg);
@@ -335,6 +436,13 @@ static bool parse_args(int argc, char *argv[]) 
				goto err;

			}

			break;

		case 'm':

			test_args.migration_freq_ms = atoi(optarg);

			if (test_args.migration_freq_ms < 0) {

				pr_info("0 or positive value needed for -m\n");

				goto err;

			}

			break;

		case 'h':

		default:

			goto err;
@@ -358,6 +466,11 @@ int main(int argc, char *argv[]) 
	if (!parse_args(argc, argv))

		exit(KSFT_SKIP);



	if (test_args.migration_freq_ms && get_nprocs() < 2) {

		print_skip("At least two physical CPUs needed for vCPU migration");

		exit(KSFT_SKIP);

	}



	vm = test_vm_create();

	test_run(vm);

	kvm_vm_free(vm);