Re: [kvm-unit-tests PATCH v4 6/9] s390x: smp: Loop if secondary cpu returns into cpu setup again

[David Hildenbrand <david@redhat.com>]

On 21.01.20 14:42, Janosch Frank wrote:
> Up to now a secondary cpu could have returned from the function it was
> executing and ending up somewhere in cstart64.S. This was mostly
> circumvented by an endless loop in the function that it executed.
> 
> Let's add a loop to the end of the cpu setup, so we don't have to rely
> on added loops in the tests.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
>  s390x/cstart64.S | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/s390x/cstart64.S b/s390x/cstart64.S
> index 9af6bb3..5fd8d2f 100644
> --- a/s390x/cstart64.S
> +++ b/s390x/cstart64.S
> @@ -162,6 +162,8 @@ smp_cpu_setup_state:
>  	/* We should only go once through cpu setup and not for every restart */
>  	stg	%r14, GEN_LC_RESTART_NEW_PSW + 8
>  	br	%r14
> +	/* If the function returns, just loop here */
> +0:	j	0
>  
>  pgm_int:
>  	SAVE_REGS
> 

This patch collides with a patch I have still queued

Author: Janosch Frank <frankja@linux.ibm.com>
Date:   Wed Dec 11 06:59:22 2019 -0500

    s390x: smp: Use full PSW to bringup new cpu
    
    Up to now we ignored the psw mask and only used the psw address when
    bringing up a new cpu. For DAT we need to also load the mask, so let's
    do that.
    
    Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
    Reviewed-by: David Hildenbrand <david@redhat.com>
    Message-Id: <20191211115923.9191-2-frankja@linux.ibm.com>
    Signed-off-by: David Hildenbrand <david@redhat.com>


In that patch we use a lpswe to jump to the target code, not a br. So the
return address will no longer be stored in %14 and this code here would stop working
AFAIKS.

Shall I drop that patch for now?

-- 
Thanks,

David / dhildenb