Re: [PATCH 0/4] hw/s390x: Alias @dump-skeys -> @dump-s390-skey and deprecate

[Dr. David Alan Gilbert]

* Thomas Huth (thuth@redhat.com) wrote:
> On 30/05/2024 09.45, Philippe Mathieu-Daudé wrote:
> > We are trying to unify all qemu-system-FOO to a single binary.
> > In order to do that we need to remove QAPI target specific code.
> > 
> > @dump-skeys is only available on qemu-system-s390x. This series
> > rename it as @dump-s390-skey, making it available on other
> > binaries. We take care of backward compatibility via deprecation.
> > 
> > Philippe Mathieu-Daudé (4):
> >    hw/s390x: Introduce the @dump-s390-skeys QMP command
> >    hw/s390x: Introduce the 'dump_s390_skeys' HMP command
> >    hw/s390x: Deprecate the HMP 'dump_skeys' command
> >    hw/s390x: Deprecate the QMP @dump-skeys command
> 
> Why do we have to rename the command? Just for the sake of it? I think
> renaming HMP commands is maybe ok, but breaking the API in QMP is something
> you should consider twice.
> 
> And even if we decide to rename ... maybe we should discuss whether it makes
> sense to come up with a generic command instead: As far as I know, ARM also
> has something similar, called MTE. Maybe we also want to dump MTE keys one
> day? So the new command should maybe be called "dump-memory-keys" instead?

I think there are at least two different concepts; but I agree it would be
nice to keep a single command for matching concepts across different 
architectures;
I can't say I know the details of any, but:

  a) Page table things - I think x86 PKRU/PKEY (???) is a page table thing
    where pages marked a special way are associated with keys.
    That sounds similar to what the skeys are???

  b) Upper bit things - where you steal a few bits from the virtual address
    and then use that to associate some security; I think that's closer
    to what MTE is isn't it?

I'm not sure the two fit in the same command.

Dave

> Or should it maybe rather be an option to the existing "dump-guest-memory"
> command instead?
> 
>  Thomas
> 
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