Re: [PATCH 1/2] docs/about: Deprecate 32-bit x86 hosts and qemu-system-i386

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

On Tue, Feb 28, 2023 at 03:19:20AM -0500, Michael S. Tsirkin wrote:
> On Tue, Feb 28, 2023 at 08:49:09AM +0100, Thomas Huth wrote:
> > On 27/02/2023 21.12, Michael S. Tsirkin wrote:
> > > On Mon, Feb 27, 2023 at 11:50:07AM +0000, Daniel P. Berrangé wrote:
> > > > I feel like we should have separate deprecation entries for the
> > > > i686 host support, and for qemu-system-i386 emulator binary, as
> > > > although they're related they are independant features with
> > > > differing impact. eg removing qemu-system-i386 affects all
> > > > host architectures, not merely 32-bit x86 host, so I think we
> > > > can explain the impact more clearly if we separate them.
> > > 
> > > Removing qemu-system-i386 seems ok to me - I think qemu-system-x86_64 is
> > > a superset.
> > > 
> > > Removing support for building on 32 bit systems seems like a pity - it's
> > > one of a small number of ways to run 64 bit binaries on 32 bit systems,
> > > and the maintainance overhead is quite small.
> > 
> > Note: We're talking about 32-bit *x86* hosts here. Do you really think that
> > someone is still using QEMU usermode emulation
> > to run 64-bit binaries on a 32-bit x86 host?? ... If so, I'd be very surprised!
> 
> I don't know - why x86 specifically? One can build a 32 bit binary on any host.
> I think 32 bit x86 environments are just more common in the cloud.

Can you point to anything that backs up that assertion. Clouds I've
seen always give you a 64-bit environment, and many OS no longer
even ship 32-bit installable media. I would be surprised if 32-bit
is above very very low single digits usage compared to x86_64.

> > > In fact, keeping this support around forces correct use of
> > > posix APIs such as e.g. PRIx64 which makes the code base
> > > more future-proof.
> > 
> > If you're concerned about PRIx64 and friends: We still continue to do
> > compile testing with 32-bit MIPS cross-compilers and Windows 32-bit
> > cross-compilers for now. The only thing we'd lose is the 32-bit "make check"
> > run in the CI.
> > 
> >  Thomas
> 
> Yes - fundamentally 32 bit does not seem that different from e.g.
> windows builds - we presumably support these but AFAIK CI does not
> test these.

We do compile test windows in CI via mingw, and we also do build
and unit tests via msys.

Even Windows has dropped 32-bit support though, and so the only
reason we keep 32-bit Windows around is because of Windows 10.
Once a Windows 12 comes along, we'll not need to support 32-bit
Windows either.

With regards,
Daniel
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