Re: [PATCH v2 4/7] s390/physmem_info: query diag500(STORAGE LIMIT) to support QEMU/KVM memory devices

[Halil Pasic <pasic@linux.ibm.com>]

On Tue, 15 Oct 2024 11:01:44 -0400
Eric Farman <farman@linux.ibm.com> wrote:

> > +		  [subcode] "i" (DIAG500_SC_STOR_LIMIT)
> > +		: "memory", "1", "2");
> > +	if (!storage_limit)
> > +		return -EINVAL;
> > +	/* Convert inclusive end to exclusive end */
> > +	*max_physmem_end = storage_limit + 1;
> >  	return 0;
> >  }
> >  
> >   
> 
> I like the idea of a defined constant here instead of hardcoded, but maybe it should be placed
> somewhere in include/uapi so that QEMU can pick it up with update-linux-headers.sh and be in sync
> with the kernel, instead of just an equivalent definition in [1] ?
> 
> [1] https://lore.kernel.org/qemu-devel/20241008105455.2302628-8-david@redhat.com/

I think it is fine to have equivalent definitions. This is more or less
an ISA thing we are introducing here. And IMHO it would be fine to have
such a definition even if the emulator was supposed to run on an OS that
is not Linux and without without KVM.

Regards,
Halil