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

Janosch Frank
2022-03-04T10:56:50Z

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;
> /*