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

["Michael S. Tsirkin" <mst@xxxxxxxxxx>]

On Tue, Feb 28, 2023 at 08:59:52AM +0000, Daniel P. Berrangé wrote:
> 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.


Sorry about being unclear. I meant that it seems easier to run CI in the
cloud in a 32 bit x64 environment than get a 32 bit ARM environment.

> I would be surprised if 32-bit
> is above very very low single digits usage compared to x86_64.

Absolutely.

> > > > 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

Or maybe we'll just rely on WSL.

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