Re: [PATCH v5 23/23] xen/README: add compiler and binutils versions for RISC-V64

[Julien Grall <julien@xxxxxxx>]

Hi Jan,

On 27/02/2024 07:55, Jan Beulich wrote:
> On 26.02.2024 18:39, Oleksii Kurochko wrote:
> > This patch doesn't represent a strict lower bound for GCC and
> > GNU Binutils; rather, these versions are specifically employed by
> > the Xen RISC-V container and are anticipated to undergo continuous
> > testing.
> Up and until that container would be updated to a newer gcc. I'm
> afraid I view this as too weak a criteria,
I disagree. We have to decide a limit at some point. It is sensible to 
say that we are only supporting what we can tests. AFAIK, this is what 
QEMU has been doing.
> but I'm also not meaning to
> stand in the way if somebody else wants to ack this patch in this form;
> my bare minimum requirement is now met.
>
> > --- a/README
> > +++ b/README
> > @@ -48,6 +48,15 @@ provided by your OS distributor:
> >         - For ARM 64-bit:
> >           - GCC 5.1 or later
> >           - GNU Binutils 2.24 or later
> > +      - For RISC-V 64-bit:
> > +        - GCC 12.2 or later
> > +        - GNU Binutils 2.39 or later
> > +        This doesn't represent a strict lower bound for GCC and GNU Binutils;
> > +        rather, these versions are specifically employed by the Xen RISC-V
> > +        container and are anticipated to undergo continuous testing.
> As per above, I think here it really needs saying "at the time of writing"
> or recording a concrete date. Furthermore I expect "these versions" relates
> to the specifically named versions and particularly _not_ to "or later":
> With the criteria you apply, using later versions (or in fact any version
> other than the very specific ones used in the container) would be similarly
> untested. Much like x86 and Arm don't have the full range of permitted
> tool chain versions continuously tested. Plus don't forget that distros may
> apply their own selection of patches on top of what they take from upstream
> (and they may also take random snapshots rather than released versions).
TBH, I think this should be dropped from the README. With the wording, 
it implies that older GCC would work, but this is not a guarantee.
The same for Arm, I suspect some revision of GCC below 5.1 that may 
work. But that's just convenience to list a lower limit.
With the sentence dropped, I would be happy to ack this patch.

> IOW it is hard for me to see why RISC-V needs stronger restrictions here
> than other architectures. It ought to be possible to determine a baseline
> version. Even if taking the desire to have "pause" available as a
> requirement, gas (and presumably gld) 2.36.1 would already suffice.
I think we want to bump it on Arm. There are zero reasons to try to keep 
a lower versions if nobody tests/use it in production.
I would suggest to do the same on x86. What's the point of try to 
support Xen with a 15+ years old compiler?
Cheers,

--
Julien Grall