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

[Heiko Carstens]

On Tue, Oct 15, 2024 at 11:01:44AM -0400, Eric Farman wrote:
> On Mon, 2024-10-14 at 20:43 +0200, Heiko Carstens wrote:
> > On Mon, Oct 14, 2024 at 04:46:16PM +0200, David Hildenbrand wrote:
...
> > +#define DIAG500_SC_STOR_LIMIT 4
...
> 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@xxxxxxxxxx/

It is already a mess; we have already subcode 3 defined:

#define KVM_S390_VIRTIO_CCW_NOTIFY 3

in

arch/s390/include/uapi/asm/virtio-ccw.h

which for some reason is uapi. But it doesn't make sense to put the
new subcode 4 there too. So what is the end result?

Another uapi file? I think resolving this would be a project on its own.