Re: [qemu-s390x] [PATCH v5 2/2] s390: diagnose 318 info reset and migration support

[Cornelia Huck]

On Wed, 26 Jun 2019 11:12:04 +0200
Christian Borntraeger <address@hidden> wrote:

> 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
> 

Yes, that's what I remember as well... and printing/logging a warning
is a good idea.