Re: [kvm-unit-tests PATCH 1/1] s390x: sclp: consider monoprocessor on read_info error

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Mon, 24 Apr 2023 19:42:18 +0200
Pierre Morel <pmorel@linux.ibm.com> wrote:

> When we can not read SCP information we can not abort during
> sclp_get_cpu_num() because this function is called during exit
> and calling it will lead to an infnite loop.
> 
> The loop is:
> abort() -> exit() -> smp_teardown() -> smp_query_num_cpus() ->
> sclp_get_cpu_num() -> assert() -> abort()
> 
> Since smp_setup() is done after sclp_read_info() inside setup() this
> loop happens when only the start processor is running.
> Let sclp_get_cpu_num() return 1 in this case.

looks good to me, but please add a comment to explain that this is only
supposed to happen in exceptional circumstances

> 
> Fixes: 52076a63d569 ("s390x: Consolidate sclp read info")
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> ---
>  lib/s390x/sclp.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/s390x/sclp.c b/lib/s390x/sclp.c
> index acdc8a9..c09360d 100644
> --- a/lib/s390x/sclp.c
> +++ b/lib/s390x/sclp.c
> @@ -119,8 +119,9 @@ void sclp_read_info(void)
>  
>  int sclp_get_cpu_num(void)
>  {
> -	assert(read_info);
> -	return read_info->entries_cpu;
> +    if (read_info)
> +	    return read_info->entries_cpu;
> +    return 1;
>  }
>  
>  CPUEntry *sclp_get_cpu_entries(void)