Re: [kvm-unit-tests PATCH v2 0/1] s390x: do not enable PV dump support by default

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Wed, 19 Oct 2022 17:47:36 +0200
Janosch Frank <frankja@linux.ibm.com> wrote:

> On 10/19/22 17:19, Claudio Imbrenda wrote:
> > On Wed, 19 Oct 2022 16:53:19 +0200
> > Nico Boehr <nrb@linux.ibm.com> wrote:
> >   
> >> v1->v2:
> >> ---
> >> * add indent to CONFIG_DUMP if in Makefile (thanks Janosch)
> >> * add comment (thanks Janosch)
> >>
> >> Currently, dump support is always enabled by setting the respective
> >> plaintext control flag (PCF). Unfortunately, older machines without
> >> support for PV dump will not start the guest when this PCF is set.  
> > 
> > maybe for the long term we could try to fix the stub generated by
> > genprotimg to check the plaintext flags and the available features and
> > refuse to try to start if the required features are missing.  
> 
> That's not possible on multiple levels:
> * Unsecure G2 does not have stfle 158
> * Dump is a host feature so I'm unsure if it would even be indicated in 
> the guest

fair enough. maybe those are problems that can be somehow fixed in the
(far) future.

for example when loading the blob with diag 308 subcode 8, the host
could reject it with an appropriate error code (since it would fail
to boot anyway)

not something we have to worry about now, though

> 
> > 
> > ideally providing a custom message when generating the image, to be
> > shown if the required features are missing. e.g. for kvm unit test, the
> > custom message could be something like
> > SKIP: $TEST_NAME: Missing hardware features
> > 
> > once that is in place, we could revert this patch  
> 
> Also the host that's using genprotimg might not be PV enabled or even 
> s390x so checking on image generation is no option either.

checking at image generation time is exactly what I did not want.

> 
> >   
> >>
> >> Nico Boehr (1):
> >>    s390x: do not enable PV dump support by default
> >>
> >>   configure      | 11 +++++++++++
> >>   s390x/Makefile | 26 +++++++++++++++++---------
> >>   2 files changed, 28 insertions(+), 9 deletions(-)
> >>  
> >   
>