Re: [PATCH kvm-unit-tests v1 6/6] lib: s390x: smp: Convert remaining smp_sigp to _retry

[Janosch Frank <frankja@linux.ibm.com>]

On 3/3/22 22:04, Eric Farman wrote:
> A SIGP SENSE is used to determine if a CPU is stopped or operating,
> and thus has a vested interest in ensuring it received a CC0 or CC1,
> instead of a CC2 (BUSY). But, any order could receive a CC2 response,
> and is probably ill-equipped to respond to it.

sigp sense running status doesn't return a cc2, only sigp sense does afaik.
Looking at the KVM implementation tells me that it's not doing more than 
looking at the R bit in the sblk.

> 
> In practice, the order is likely to only encounter this when racing
> with a SIGP STOP (AND STORE STATUS) or SIGP RESTART order, which are
> unlikely. But, since it's not impossible, let's convert the library
> calls that issue a SIGP to loop on CC2 so the callers do not need
> to react to that possible outcome.
> 
> Signed-off-by: Eric Farman <farman@linux.ibm.com>
> ---
>   lib/s390x/smp.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/s390x/smp.c b/lib/s390x/smp.c
> index 85b046a5..2e476264 100644
> --- a/lib/s390x/smp.c
> +++ b/lib/s390x/smp.c
> @@ -85,7 +85,7 @@ bool smp_cpu_stopped(uint16_t idx)
>   
>   bool smp_sense_running_status(uint16_t idx)
>   {
> -	if (smp_sigp(idx, SIGP_SENSE_RUNNING, 0, NULL) != SIGP_CC_STATUS_STORED)
> +	if (smp_sigp_retry(idx, SIGP_SENSE_RUNNING, 0, NULL) != SIGP_CC_STATUS_STORED)
>   		return true;
>   	/* Status stored condition code is equivalent to cpu not running. */
>   	return false;
> @@ -169,7 +169,7 @@ static int smp_cpu_restart_nolock(uint16_t idx, struct psw *psw)
>   	 * running after the restart.
>   	 */
>   	smp_cpu_stop_nolock(idx, false);
> -	rc = smp_sigp(idx, SIGP_RESTART, 0, NULL);
> +	rc = smp_sigp_retry(idx, SIGP_RESTART, 0, NULL);
>   	if (rc)
>   		return rc;
>   	/*