Re: dropping 32-bit Windows host support

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

On Mon, Feb 19, 2024 at 04:40:38PM +0000, Peter Maydell wrote:
> On Mon, 19 Feb 2024 at 16:26, Thomas Huth <thuth@redhat.com> wrote:
> >
> > On 19/02/2024 16.53, Daniel P. Berrangé wrote:
> > > On Mon, Feb 19, 2024 at 03:37:31PM +0000, Peter Maydell wrote:
> > >> Our msys2 32-bit Windows host CI job has been failing recently
> > >> because upstream MSYS2 are starting to phase out 32-bit windows
> > >> host support and are steadily removing i686 versions of packages.
> > >> The latest is dtc:
> > >> https://gitlab.com/qemu-project/qemu/-/issues/2177
> > >>
> > >> The writing is clearly on the wall for their 32-bit support, judging
> > >> from the "2023-12-13 - Starting to drop some 32-bit Packages" news
> > >> item at https://www.msys2.org/news/ and associated discussion at
> > >> https://github.com/msys2/MINGW-packages/discussions/19326 .
> > >>
> > >> QEMU on a 32-bit host is not likely to be a great experience, and I
> > >> suspect we don't have many users using 32-bit Windows who couldn't
> > >> use the 64-bit version instead. Our Download page points users at
> > >> MSYS2's packages, and they have already dropped the 32-bit QEMU
> > >> package build. Stefan Weil's binaries page, which is the other thing
> > >> we link to from Download, has no 32-bit version newer than 7.2.0.
> > >> So anybody using 32-bit Windows QEMU must be building it themselves.
> > >> Plus, we've already deprecated system emulation on 32-bit x86 hosts,
> > >> so the only remaining "supported" config is with the NVMM or WHPX
> > >> accelerators.
> > >
> > > The other data point is that Win11 is 64-bit only, and IIUC,
> > > Win10 was 64-bit only for new OEM installs too, only upgrades
> > > or end user installs could choose 32-bit.
> >
> > Yes, and considering that there will likely be a Windows 12 at one point in
> > time, we'll drop support for Win10 and thus 32-bit support anyway.
> >
> > >> I suggest that we should:
> > >>
> > >>   * remove the msys2-32bit CI job entirely (we will still have at least
> > >>     compile-time coverage via the cross-win32-system job)
> > >>   * document that the 32-bit Windows support is deprecated in
> > >>     docs/about/build-platforms.rst and deprecated.rst
> > >>   * update our Download page to remove mention of 32-bit Windows
> > >>
> > >> Any objections?
> > >
> > > I think that's sane.
> >
> > Sounds good to me, too.
> >
> > Note that we already have an entry for "System emulation on 32-bit x86
> > hosts" in the deprecation list ... so IMHO we could also justify to drop the
> > 32-bit Windows support immediately, since that's a subset of that entry.
> 
> Mmm. I had initially misread that as only applying to TCG,
> but it's more general than that. So I think I agree that we
> should go ahead and mark 32-bit Windows support as definitively
> dropped.

Technically our existing deprecation would still allow for 32-bit
builds of qemu-img, qemu-io, etc tools, on Windows, but that's
very niche. 


With regards,
Daniel
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