Re: [PATCH v4 11/11] KVM: selftests: Enable tunning of err_margin_us in arch timer test

Anup Patel
2023-12-14T06:44:34Z

Hi Marc, Hi Oliver,

On Tue, Dec 12, 2023 at 2:52 PM Haibo Xu <haibo1.xu@intel.com> wrote:
>
> There are intermittent failures occured when stressing the
> arch-timer test in a Qemu VM:
>
> Guest assert failed, vcpu 0; stage; 4; iter: 3
> ==== Test Assertion Failure ====
> aarch64/arch_timer.c:196: config_iter + 1 == irq_iter
> pid=4048 tid=4049 errno=4 - Interrupted system call
> 1 0x000000000040253b: test_vcpu_run at arch_timer.c:248
> 2 0x0000ffffb60dd5c7: ?? ??:0
> 3 0x0000ffffb6145d1b: ?? ??:0
> 0x3 != 0x2 (config_iter + 1 != irq_iter)e
>
> Further test and debug show that the timeout for an interrupt
> to arrive do have random high fluctuation, espectially when
> testing in an virtual environment.
>
> To alleviate this issue, just expose the timeout value as user
> configurable and print some hint message to increase the value
> when hitting the failure..
>
> Signed-off-by: Haibo Xu <haibo1.xu@intel.com>

Can you please review this patch ?

We want to take this entire series through the KVM RISC-V tree.

Regards,
Anup

> ---
> .../selftests/kvm/aarch64/arch_timer.c | 8 +++++--
> tools/testing/selftests/kvm/arch_timer.c | 22 +++++++++++++------
> .../selftests/kvm/include/timer_test.h | 1 +
> .../testing/selftests/kvm/riscv/arch_timer.c | 8 +++++--
> 4 files changed, 28 insertions(+), 11 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/aarch64/arch_timer.c b/tools/testing/selftests/kvm/aarch64/arch_timer.c
> index 4b421d421c3f..139eecbf77e7 100644
> --- a/tools/testing/selftests/kvm/aarch64/arch_timer.c
> +++ b/tools/testing/selftests/kvm/aarch64/arch_timer.c
> @@ -131,10 +131,14 @@ static void guest_run_stage(struct test_vcpu_shared_data *shared_data,
>
> /* Setup a timeout for the interrupt to arrive */
> udelay(msecs_to_usecs(test_args.timer_period_ms) +
> - TIMER_TEST_ERR_MARGIN_US);
> + test_args.timer_err_margin_us);
>
> irq_iter = READ_ONCE(shared_data->nr_iter);
> - GUEST_ASSERT_EQ(config_iter + 1, irq_iter);
> + __GUEST_ASSERT(config_iter + 1 == irq_iter,
> + "config_iter + 1 = 0x%lx, irq_iter = 0x%lx.\n"
> + " Guest timer interrupt was not trigged within the specified\n"
> + " interval, try to increase the error margin by [-e] option.\n",
> + config_iter + 1, irq_iter);
> }
> }
>
> diff --git a/tools/testing/selftests/kvm/arch_timer.c b/tools/testing/selftests/kvm/arch_timer.c
> index 60963fce16f2..5050022fd345 100644
> --- a/tools/testing/selftests/kvm/arch_timer.c
> +++ b/tools/testing/selftests/kvm/arch_timer.c
> @@ -5,16 +5,17 @@
> * The guest's main thread configures the timer interrupt and waits
> * for it to fire, with a timeout equal to the timer period.
> * It asserts that the timeout doesn't exceed the timer period plus
> - * an error margin of 100us.
> + * an user configurable error margin(default to 100us).
> *
> * On the other hand, upon receipt of an interrupt, the guest's interrupt
> * handler validates the interrupt by checking if the architectural state
> * is in compliance with the specifications.
> *
> * 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.
> + * period (-p), number of vCPUs (-n), iterations per stage (-i), and timer
> + * interrupt arrival error margin (-e). 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.
> */
> @@ -34,6 +35,7 @@ struct test_args test_args = {
> .nr_iter = NR_TEST_ITERS_DEF,
> .timer_period_ms = TIMER_TEST_PERIOD_MS_DEF,
> .migration_freq_ms = TIMER_TEST_MIGRATION_FREQ_MS,
> + .timer_err_margin_us = TIMER_TEST_ERR_MARGIN_US,
> .reserved = 1,
> };
>
> @@ -179,8 +181,9 @@ static void test_run(struct kvm_vm *vm)
>
> static void test_print_help(char *name)
> {
> - pr_info("Usage: %s [-h] [-n nr_vcpus] [-i iterations] [-p timer_period_ms]\n",
> - name);
> + pr_info("Usage: %s [-h] [-n nr_vcpus] [-i iterations] [-p timer_period_ms]\n"
> + "\t\t [-m migration_freq_ms] [-o counter_offset]\n"
> + "\t\t [-e timer_err_margin_us]\n", name);
> pr_info("\t-n: Number of vCPUs to configure (default: %u; max: %u)\n",
> NR_VCPUS_DEF, KVM_MAX_VCPUS);
> pr_info("\t-i: Number of iterations per stage (default: %u)\n",
> @@ -190,6 +193,8 @@ static void test_print_help(char *name)
> 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-o: Counter offset (in counter cycles, default: 0) [aarch64-only]\n");
> + pr_info("\t-e: Interrupt arrival error margin(in us) of the guest timer (default: %u)\n",
> + TIMER_TEST_ERR_MARGIN_US);
> pr_info("\t-h: print this help screen\n");
> }
>
> @@ -197,7 +202,7 @@ static bool parse_args(int argc, char *argv[])
> {
> int opt;
>
> - while ((opt = getopt(argc, argv, "hn:i:p:m:o:")) != -1) {
> + while ((opt = getopt(argc, argv, "hn:i:p:m:o:e:")) != -1) {
> switch (opt) {
> case 'n':
> test_args.nr_vcpus = atoi_positive("Number of vCPUs", optarg);
> @@ -216,6 +221,9 @@ static bool parse_args(int argc, char *argv[])
> case 'm':
> test_args.migration_freq_ms = atoi_non_negative("Frequency", optarg);
> break;
> + case 'e':
> + test_args.timer_err_margin_us = atoi_non_negative("Error Margin", optarg);
> + break;
> case 'o':
> test_args.counter_offset = strtol(optarg, NULL, 0);
> test_args.reserved = 0;
> diff --git a/tools/testing/selftests/kvm/include/timer_test.h b/tools/testing/selftests/kvm/include/timer_test.h
> index 968257b893a7..b1d405e7157d 100644
> --- a/tools/testing/selftests/kvm/include/timer_test.h
> +++ b/tools/testing/selftests/kvm/include/timer_test.h
> @@ -22,6 +22,7 @@ struct test_args {
> int nr_iter;
> int timer_period_ms;
> int migration_freq_ms;
> + int timer_err_margin_us;
> /* Members of struct kvm_arm_counter_offset */
> uint64_t counter_offset;
> uint64_t reserved;
> diff --git a/tools/testing/selftests/kvm/riscv/arch_timer.c b/tools/testing/selftests/kvm/riscv/arch_timer.c
> index 13bf184d1ff5..45a139dc7ce3 100644
> --- a/tools/testing/selftests/kvm/riscv/arch_timer.c
> +++ b/tools/testing/selftests/kvm/riscv/arch_timer.c
> @@ -55,10 +55,14 @@ static void guest_run(struct test_vcpu_shared_data *shared_data)
>
> /* Setup a timeout for the interrupt to arrive */
> udelay(msecs_to_usecs(test_args.timer_period_ms) +
> - TIMER_TEST_ERR_MARGIN_US);
> + test_args.timer_err_margin_us);
>
> irq_iter = READ_ONCE(shared_data->nr_iter);
> - GUEST_ASSERT_EQ(config_iter + 1, irq_iter);
> + __GUEST_ASSERT(config_iter + 1 == irq_iter,
> + "config_iter + 1 = 0x%lx, irq_iter = 0x%lx.\n"
> + " Guest timer interrupt was not trigged within the specified\n"
> + " interval, try to increase the error margin by [-e] option.\n",
> + config_iter + 1, irq_iter);
> }
> }
>
> --
> 2.34.1
>