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().
--
Thanks,
David / dhildenb
