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Message-Id: <20210901211412.4171835-13-rananta@google.com>
Date: Wed, 1 Sep 2021 21:14:12 +0000
From: Raghavendra Rao Ananta <rananta@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
James Morse <james.morse@....com>,
Alexandru Elisei <alexandru.elisei@....com>,
Suzuki K Poulose <suzuki.poulose@....com>
Cc: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>, Peter Shier <pshier@...gle.com>,
Ricardo Koller <ricarkol@...gle.com>,
Oliver Upton <oupton@...gle.com>,
Reiji Watanabe <reijiw@...gle.com>,
Jing Zhang <jingzhangos@...gle.com>,
Raghavendra Rao Anata <rananta@...gle.com>,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: [PATCH v3 12/12] 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 3134cc8beb69d0d
("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@...gle.com>
---
.../selftests/kvm/aarch64/arch_timer.c | 108 +++++++++++++++++-
1 file changed, 107 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/kvm/aarch64/arch_timer.c b/tools/testing/selftests/kvm/aarch64/arch_timer.c
index 1383f33850e9..de246c7afab2 100644
--- a/tools/testing/selftests/kvm/aarch64/arch_timer.c
+++ b/tools/testing/selftests/kvm/aarch64/arch_timer.c
@@ -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"
@@ -41,12 +45,14 @@ 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 = 0, /* Turn off migrations by default */
};
#define msecs_to_usecs(msec) ((msec) * 1000LL)
@@ -81,6 +87,9 @@ struct test_vcpu {
static struct test_vcpu test_vcpu[KVM_MAX_VCPUS];
static struct test_vcpu_shared_data vcpu_shared_data[KVM_MAX_VCPUS];
+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)
{
@@ -216,6 +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:
@@ -235,9 +249,73 @@ 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);
+ 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_alloc(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,
@@ -245,8 +323,23 @@ 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 struct kvm_vm *test_vm_create(void)
@@ -286,6 +379,7 @@ 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: 0)\n");
pr_info("\t-h: print this help screen\n");
}
@@ -293,7 +387,7 @@ 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);
@@ -320,6 +414,13 @@ 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;
@@ -343,6 +444,11 @@ int main(int argc, char *argv[])
if (!parse_args(argc, argv))
exit(KSFT_SKIP);
+ if (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);
--
2.33.0.153.gba50c8fa24-goog
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