Re: [Qemu-devel] [qemu-s390x] [PATCH] s390-bios: Skip bootmap signature entries

[Cornelia Huck <cohuck@redhat.com>]

On Mon, 6 May 2019 13:13:55 +0200
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> On 06.05.19 13:05, Cornelia Huck wrote:
> > On Mon, 6 May 2019 12:46:50 +0200
> > Christian Borntraeger <borntraeger@de.ibm.com> wrote:
> >   
> >> On 06.05.19 12:34, Cornelia Huck wrote:  
> >>> On Mon, 6 May 2019 12:18:42 +0200
> >>> Christian Borntraeger <borntraeger@de.ibm.com> wrote:  
> >   
> >>>> I think we should not. Those entries might have sematic elements that the guest
> >>>> wants to enforce. I do not think that this will come, but imagine a boot entry
> >>>> that mandates some security wishes (e.g. do only run on non-shared cores).    
> >>>
> >>> Can we split the namespace for BOOT_SCRIPT into 'ignore if you don't
> >>> know what that is' and 'fail if you don't know what that is'? I'm
> >>> completely confused how 'optional' those entries are supposed to be...    
> >>
> >> Since we do not know if and what future entries will come the current default
> >> of failing seems the best approach. We can then add things to pc-bios when
> >> necessary.  
> > 
> > That's where I'm coming from: Have some values where unknown entries
> > lead to (desired) failure, and others where unknown entries are simply
> > ignored. That would give us automatic toleration for optional entries.  
> 
> Well, this is the first new entry after 14 years of list-directed-ipl so there
> is a slight chance to over-engineer here ;-)
> 
> In the end this is a field that does not belong to Linux-only, it is also defined
> by the machine architecture.

Yeah, I understand that having to get this into the main architecture
makes this harder to change.

If there is nothing coming in the foreseeable future that would need
toleration (and not failure), it's probably not worth spending more
time on that and we should just go with this patch.

I'd recommend putting this (+ a rebuild) into stable as well, though,
so that at least 4.0-stable will tolerate signatures. (Distros
backporting this would be a good idea as well.)