On 30.03.20 12:58, David Hildenbrand wrote:
> On 30.03.20 10:49, Christian Borntraeger wrote:
>> make sure that sigp sense running status returns a sane value for
>> stopped CPUs.
>>
>> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
>> ---
>> lib/s390x/smp.c | 2 +-
>> lib/s390x/smp.h | 2 +-
>> s390x/smp.c | 11 +++++++++++
>> 3 files changed, 13 insertions(+), 2 deletions(-)
>>
>> diff --git a/lib/s390x/smp.c b/lib/s390x/smp.c
>> index 5ed8b7b..492cb05 100644
>> --- a/lib/s390x/smp.c
>> +++ b/lib/s390x/smp.c
>> @@ -58,7 +58,7 @@ bool smp_cpu_stopped(uint16_t addr)
>> return !!(status & (SIGP_STATUS_CHECK_STOP|SIGP_STATUS_STOPPED));
>> }
>>
>> -bool smp_cpu_running(uint16_t addr)
>> +bool smp_sense_running_status(uint16_t addr)
>> {
>> if (sigp(addr, SIGP_SENSE_RUNNING, 0, NULL) != SIGP_CC_STATUS_STORED)
>> return true;
>> diff --git a/lib/s390x/smp.h b/lib/s390x/smp.h
>> index a8b98c0..639ec92 100644
>> --- a/lib/s390x/smp.h
>> +++ b/lib/s390x/smp.h
>> @@ -40,7 +40,7 @@ struct cpu_status {
>> int smp_query_num_cpus(void);
>> struct cpu *smp_cpu_from_addr(uint16_t addr);
>> bool smp_cpu_stopped(uint16_t addr);
>> -bool smp_cpu_running(uint16_t addr);
>> +bool smp_sense_running_status(uint16_t addr);
>> int smp_cpu_restart(uint16_t addr);
>> int smp_cpu_start(uint16_t addr, struct psw psw);
>> int smp_cpu_stop(uint16_t addr);
>> diff --git a/s390x/smp.c b/s390x/smp.c
>> index 79cdc1f..f9f143d 100644
>> --- a/s390x/smp.c
>> +++ b/s390x/smp.c
>> @@ -210,6 +210,16 @@ static void test_emcall(void)
>> report_prefix_pop();
>> }
>>
>> +static void test_sense_running(void)
>> +{
>> + report_prefix_push("sense_running");
>> + /* make sure CPU is stopped */
>> + smp_cpu_stop(1);
>> + report(!smp_sense_running_status(1), "CPU1 sense claims not running");
>> + report_prefix_pop();
>> +}
>> +
>> +
>> /* Used to dirty registers of cpu #1 before it is reset */
>> static void test_func_initial(void)
>> {
>> @@ -319,6 +329,7 @@ int main(void)
>> test_store_status();
>> test_ecall();
>> test_emcall();
>> + test_sense_running();
>> test_reset();
>> test_reset_initial();
>> smp_cpu_destroy(1);
>>
>
> In kvm, we set/clear via kvm_arch_vcpu_load/kvm_arch_vcpu_put. This
> means, that a VCPU will also be indicated as running, in case we perform
> certain VCPU IOCTLs, while the VCPU is already stopped.
>
> Especially, there is a theoretical race between stopping a VCPU, and it
> still being in the kernel, and the other thread sensing the running
> status. This is the case with !kvm_s390_user_cpu_state_ctrl(), when
> leaving handle_stop() but also with kvm_s390_user_cpu_state_ctrl(), when
> setting the MP state via kvm_arch_vcpu_ioctl_set_mpstate().
I think I will just busy wait until the target is not running. This must happen and a timeout indicates a failure.
