Re: [PATCH v3 11/26] target/arm/kvm-rme: Add measurement algorithm property

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Nov 26, 2024 at 04:11:19PM +0100, Markus Armbruster wrote:
> Daniel P. Berrangé <berrange@redhat.com> writes:
> 
> > On Mon, Nov 25, 2024 at 07:56:10PM +0000, Jean-Philippe Brucker wrote:
> 
> [...]
> 
> >> diff --git a/qapi/qom.json b/qapi/qom.json
> >> index f982850bca..901ba67634 100644
> >> --- a/qapi/qom.json
> >> +++ b/qapi/qom.json
> >> @@ -1068,6 +1068,20 @@
> >>    'data': { '*cpu-affinity': ['uint16'],
> >>              '*node-affinity': ['uint16'] } }
> >>  
> >> +##
> >> +# @RmeGuestMeasurementAlgorithm:
> >> +#
> >> +# @sha256: Use the SHA256 algorithm
> >> +#
> >> +# @sha512: Use the SHA512 algorithm
> >> +#
> >> +# Algorithm to use for realm measurements
> >> +#
> >> +# Since: 9.3
> >> +##
> >> +{ 'enum': 'RmeGuestMeasurementAlgorithm',
> >> +  'data': ['sha256', 'sha512'] }
> >
> >
> > A design question for Markus....
> >
> >
> > We have a "QCryptoHashAlg" enum that covers both of these strings
> > and more besides.
> >
> > We have a choice of using a dedicated enum strictly limited to
> > just what RME needs, vs using the common enum type, but rejecting
> > unsupported algorithms at runtime.  Do we prefer duplication for
> > improve specificity, or removal of duplication ?
> 
> With a dedicated enum, introspection shows precisely the accepted
> values.
> 
> If we reuse a wider enum, introspection shows additional, invalid
> values.
> 
> Say we later make one of these valid here.  If we reuse the wider enum
> now, nothing changes in introspection then, i.e. introspection cannot
> tell us whether this particular QEMU supports this additional algorithm.
> With a dedicated enum, it can.  Whether that's needed in practice I find
> hard to predict.
> 
> I lean towards lean towards dedicated enum.
> 
> Questions?

That's fine with me. Lets stick with the approach in this patch.


With regards,
Daniel
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