Re: [Qemu-devel] [PATCH v5 2/2] s390: diagnose 318 info reset and migration support

[Christian Borntraeger]

On 25.06.19 17:17, Collin Walling wrote:
> index a606547..4c26754 100644
> --- a/target/s390x/cpu.h
> +++ b/target/s390x/cpu.h
> @@ -39,7 +39,13 @@
>  
>  #define MMU_USER_IDX 0
>  
> -#define S390_MAX_CPUS 248
> +/*
> + * HACK: The introduction of additional facility bytes in the Read Info
> + * struct consumes space used for CPU entries, thus we must reduce the
> + * original maximum CPUs of 248 by one for each new byte or risk smashing
> + * the stack.
> + */
> +#define S390_MAX_CPUS 247

I think we decided to not change that. Only if the cpu model contains the 
diag318
feature we are limited to 247 but only for the sclp response.
So we said: 
- we continue to allow 248 cpus
- the sclp response will be limited to 247 CPUs if the feature is one
- (optional) we print a warning that the guest might not see all CPUs