[kvm-unit-tests,v4,2/9] s390x: smp: Only use smp_cpu_setup once
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Message ID 20200121134254.4570-3-frankja@linux.ibm.com
State New
Headers show
Series
  • s390x: smp: Improve smp code and reset checks
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Commit Message

Janosch Frank Jan. 21, 2020, 1:42 p.m. UTC
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(-)

Comments

David Hildenbrand Jan. 23, 2020, 1:45 p.m. UTC | #1
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.
Janosch Frank Jan. 23, 2020, 1:54 p.m. UTC | #2
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.
David Hildenbrand Jan. 23, 2020, 1:56 p.m. UTC | #3
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).
David Hildenbrand Jan. 24, 2020, 8:28 a.m. UTC | #4
On 23.01.20 14:56, David Hildenbrand wrote:
> 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).
> 

So, the test works every now and then under TCG.

It seems to work very reliably with "-smp 2"

With smp 8, it sometimes works, sometimes not.

t480s: ~/git/kvm-unit-tests (kein Branch, Rebase von s390x-prep) $
./s390x-run s390x/smp.elf -smp 8
/home/dhildenb/git/qemu/s390x-softmmu/qemu-system-s390x -nodefaults
-nographic -machine s390-ccw-virtio,accel=tcg -chardev stdio,id=con0
-device sclpconsole,chardev=con0 -kernel s390x/smp.elf -smp 8 # -initrd
/tmp/tmp.UL9ZaqoKBW
SMP: Initializing, found 8 cpus
PASS: smp: start
PASS: smp: stop
PASS: smp: stop store status: prefix
PASS: smp: stop store status: stack
PASS: smp: store status at address: running: incorrect state
PASS: smp: store status at address: running: status not written
PASS: smp: store status at address: stopped: status written
PASS: smp: ecall: ecall
PASS: smp: emcall: ecall
PASS: smp: cpu reset: cpu stopped
PASS: smp: reset initial: clear: psw
PASS: smp: reset initial: clear: prefix
PASS: smp: reset initial: clear: fpc
PASS: smp: reset initial: clear: cpu timer
PASS: smp: reset initial: clear: todpr
PASS: smp: reset initial: initialized: cr0 == 0xE0
PASS: smp: reset initial: initialized: cr14 == 0xC2000000
PASS: smp: reset initial: cpu stopped
SUMMARY: 18 tests

EXIT: STATUS=1

t480s: ~/git/kvm-unit-tests (kein Branch, Rebase von s390x-prep) $
./s390x-run s390x/smp.elf -smp 8
/home/dhildenb/git/qemu/s390x-softmmu/qemu-system-s390x -nodefaults
-nographic -machine s390-ccw-virtio,accel=tcg -chardev stdio,id=con0
-device sclpconsole,chardev=con0 -kernel s390x/smp.elf -smp 8 # -initrd
/tmp/tmp.csifrEDgnC
SMP: Initializing, found 8 cpus
PASS: smp: start
PASS: smp: stop
PASS: smp: stop store status: prefix
FAIL: smp: stop store status: stack
PASS: smp: store status at address: running: incorrect state
PASS: smp: store status at address: running: status not written
PASS: smp: store status at address: stopped: status written
[... hang]


Note that there is a previous failure for "smp: stop store status:
stack" whenever the test will hang later.
David Hildenbrand Jan. 24, 2020, 8:38 a.m. UTC | #5
On 24.01.20 09:28, David Hildenbrand wrote:
> On 23.01.20 14:56, David Hildenbrand wrote:
>> 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).
>>
> 
> So, the test works every now and then under TCG.
> 
> It seems to work very reliably with "-smp 2"
> 
> With smp 8, it sometimes works, sometimes not.
> 
> t480s: ~/git/kvm-unit-tests (kein Branch, Rebase von s390x-prep) $
> ./s390x-run s390x/smp.elf -smp 8
> /home/dhildenb/git/qemu/s390x-softmmu/qemu-system-s390x -nodefaults
> -nographic -machine s390-ccw-virtio,accel=tcg -chardev stdio,id=con0
> -device sclpconsole,chardev=con0 -kernel s390x/smp.elf -smp 8 # -initrd
> /tmp/tmp.UL9ZaqoKBW
> SMP: Initializing, found 8 cpus
> PASS: smp: start
> PASS: smp: stop
> PASS: smp: stop store status: prefix
> PASS: smp: stop store status: stack
> PASS: smp: store status at address: running: incorrect state
> PASS: smp: store status at address: running: status not written
> PASS: smp: store status at address: stopped: status written
> PASS: smp: ecall: ecall
> PASS: smp: emcall: ecall
> PASS: smp: cpu reset: cpu stopped
> PASS: smp: reset initial: clear: psw
> PASS: smp: reset initial: clear: prefix
> PASS: smp: reset initial: clear: fpc
> PASS: smp: reset initial: clear: cpu timer
> PASS: smp: reset initial: clear: todpr
> PASS: smp: reset initial: initialized: cr0 == 0xE0
> PASS: smp: reset initial: initialized: cr14 == 0xC2000000
> PASS: smp: reset initial: cpu stopped
> SUMMARY: 18 tests
> 
> EXIT: STATUS=1
> 
> t480s: ~/git/kvm-unit-tests (kein Branch, Rebase von s390x-prep) $
> ./s390x-run s390x/smp.elf -smp 8
> /home/dhildenb/git/qemu/s390x-softmmu/qemu-system-s390x -nodefaults
> -nographic -machine s390-ccw-virtio,accel=tcg -chardev stdio,id=con0
> -device sclpconsole,chardev=con0 -kernel s390x/smp.elf -smp 8 # -initrd
> /tmp/tmp.csifrEDgnC
> SMP: Initializing, found 8 cpus
> PASS: smp: start
> PASS: smp: stop
> PASS: smp: stop store status: prefix
> FAIL: smp: stop store status: stack
> PASS: smp: store status at address: running: incorrect state
> PASS: smp: store status at address: running: status not written
> PASS: smp: store status at address: stopped: status written
> [... hang]
> 
> 
> Note that there is a previous failure for "smp: stop store status:
> stack" whenever the test will hang later.
> 
> 

In smp_cpu_stop_nolock(), when you do a SIGP_STOP_AND_STORE_STATUS, you
wait until the target CPU is stopped.

This does, however, not guarantee that the state has already been stored
- especially not if the target CPU is already stopped.

Stop and Store Status
The addressed CPU performs the stop function, fol-
lowed by the store-status operation (see “Store Sta-
tus” on page 4-82). The CPU does not necessarily
complete the operation, or even enter the stopped
state, during the execution of SIGNAL PROCES-
SOR ..."

So there is a race in your code. I do wonder how you can test if the
order on the target CPU has been executed, without issuing another SIGP
operation (e.g., restart) or by testing if the content to be stored was
all changed ...

Patch
diff mbox series

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();