Re: [RFC PATCH] configure: deprecate 32 bit build hosts

[Daniel P . Berrangé]

On Thu, Sep 26, 2019 at 08:50:36AM +0100, Peter Maydell wrote:
> On Thu, 26 Sep 2019 at 00:31, Alex Bennée <address@hidden> wrote:
> >
> > The 32 bit hosts are already a second class citizen especially with
> > support for running 64 bit guests under TCG. We are also limited by
> > testing as actual working 32 bit machines are getting quite rare in
> > developers personal menageries. For TCG supporting newer types like
> > Int128 is a lot harder with 32 bit calling conventions compared to
> > their larger bit sized cousins. Fundamentally address space is the
> > most useful thing for the translator to have even for a 32 bit guest a
> > 32 bit host is quite constrained.
> >
> > As far as I'm aware 32 bit KVM users are even less numerous. Even
> > ILP32 doesn't make much sense given the address space QEMU needs to
> > manage.
> 
> For KVM we should wait until the kernel chooses to drop support,
> I think.

What if the kernel is waiting for QEMU to drop support too ;-P

> > @@ -745,19 +744,22 @@ case "$cpu" in
> >    ;;
> >    armv*b|armv*l|arm)
> >      cpu="arm"
> > -    supported_cpu="yes"
> >    ;;
> 
> I'll leave others to voice opinions about their architectures,
> but I still have 32-bit arm in my test set for builds, and
> I'm pretty sure we have users (raspi users, for a start).

RHEL dropped all 32-bit host support a long time ago, so Red Hat
don't care for our products.

Fedora has recently stopped building i686 kernels and thus also no
long composes i686 installs. Some users complained, but ultimately
no one cares enough to step forward as maintainers.

That leaves armv7 as the only 32-bit arch in Fedora that is somewhat
active & maintained. I don't have any real insight on whether any
armv7 (Fedora) users are making much use of QEMU/KVM though, either
system or user emulation. 

Our preference in Fedora is to have things built on every architecture
that the distro targets, but if upstream developers explicitly drop an
architecture we're not going to try to add it back.

Regards,
Daniel
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