Re: [kvm-unit-tests PATCH v4 2/9] s390x: smp: Only use smp_cpu_setup once

David Hildenbrand
2020-01-23T13:56:35Z

On 23.01.20 14:54, Janosch Frank wrote:
> On 1/23/20 2:45 PM, David Hildenbrand wrote:
>> On 21.01.20 14:42, Janosch Frank wrote:
>>> Let's stop and start instead of using setup to run a function on a
>>> cpu.
>>>
>>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
>>> Reviewed-by: Thomas Huth <thuth@redhat.com>
>>> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>>> Acked-by: David Hildenbrand <david@redhat.com>
>>> ---
>>> s390x/smp.c | 21 ++++++++++++++-------
>>> 1 file changed, 14 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/s390x/smp.c b/s390x/smp.c
>>> index e37eb56..3e8cf3e 100644
>>> --- a/s390x/smp.c
>>> +++ b/s390x/smp.c
>>> @@ -53,7 +53,7 @@ static void test_start(void)
>>> psw.addr = (unsigned long)test_func;
>>>
>>> set_flag(0);
>>> - smp_cpu_setup(1, psw);
>>> + smp_cpu_start(1, psw);
>>> wait_for_flag();
>>> report(1, "start");
>>> }
>>> @@ -109,6 +109,7 @@ static void test_store_status(void)
>>> report(1, "status written");
>>> free_pages(status, PAGE_SIZE * 2);
>>> report_prefix_pop();
>>> + smp_cpu_stop(1);
>>>
>>> report_prefix_pop();
>>> }
>>> @@ -137,9 +138,8 @@ static void test_ecall(void)
>>>
>>> report_prefix_push("ecall");
>>> set_flag(0);
>>> - smp_cpu_destroy(1);
>>>
>>> - smp_cpu_setup(1, psw);
>>> + smp_cpu_start(1, psw);
>>> wait_for_flag();
>>> set_flag(0);
>>> sigp(1, SIGP_EXTERNAL_CALL, 0, NULL);
>>> @@ -172,9 +172,8 @@ static void test_emcall(void)
>>>
>>> report_prefix_push("emcall");
>>> set_flag(0);
>>> - smp_cpu_destroy(1);
>>>
>>> - smp_cpu_setup(1, psw);
>>> + smp_cpu_start(1, psw);
>>> wait_for_flag();
>>> set_flag(0);
>>> sigp(1, SIGP_EMERGENCY_SIGNAL, 0, NULL);
>>> @@ -192,7 +191,7 @@ static void test_reset_initial(void)
>>> psw.addr = (unsigned long)test_func;
>>>
>>> report_prefix_push("reset initial");
>>> - smp_cpu_setup(1, psw);
>>> + smp_cpu_start(1, psw);
>>>
>>> sigp_retry(1, SIGP_INITIAL_CPU_RESET, 0, NULL);
>>> sigp(1, SIGP_STORE_STATUS_AT_ADDRESS, (uintptr_t)status, NULL);
>>> @@ -223,7 +222,7 @@ static void test_reset(void)
>>> psw.addr = (unsigned long)test_func;
>>>
>>> report_prefix_push("cpu reset");
>>> - smp_cpu_setup(1, psw);
>>> + smp_cpu_start(1, psw);
>>>
>>> sigp_retry(1, SIGP_CPU_RESET, 0, NULL);
>>> report(smp_cpu_stopped(1), "cpu stopped");
>>> @@ -232,6 +231,7 @@ static void test_reset(void)
>>>
>>> int main(void)
>>> {
>>> + struct psw psw;
>>> report_prefix_push("smp");
>>>
>>> if (smp_query_num_cpus() == 1) {
>>> @@ -239,6 +239,12 @@ int main(void)
>>> goto done;
>>> }
>>>
>>> + /* Setting up the cpu to give it a stack and lowcore */
>>> + psw.mask = extract_psw_mask();
>>> + psw.addr = (unsigned long)cpu_loop;
>>> + smp_cpu_setup(1, psw);
>>> + smp_cpu_stop(1);
>>> +
>>> test_start();
>>> test_stop();
>>> test_stop_store_status();
>>> @@ -247,6 +253,7 @@ int main(void)
>>> test_emcall();
>>> test_reset();
>>> test_reset_initial();
>>> + smp_cpu_destroy(1);
>>>
>>> done:
>>> report_prefix_pop();
>>>
>>
>> With this patch, I get timeouts under TCG. Seems to loop forever.
>>
> The branch works on lpar and kvm without a problem.

Which could mean that either TCG is broken or your test is broken (e.g.,
a race condition that does not trigger under LPAR because it's faster,
or some undocumented/not guaranteed behavior).

--
Thanks,

David / dhildenb