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KVM: arm64: selftests: arch_timer: Support vCPU migration

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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 3134cc8beb
("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: Raghavendra Rao Ananta <rananta@google.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211007233439.1826892-16-rananta@google.com
This commit is contained in:
Raghavendra Rao Ananta 2021-10-07 23:34:39 +00:00 committed by Marc Zyngier
parent 4959d8650e
commit 61f6fadbf9
1 changed files with 114 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

115
tools/testing/selftests/kvm/aarch64/arch_timer.c
View File

@ -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);