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

[Richard Henderson]

On 2/27/23 01:50, Daniel P. Berrangé wrote:
> On Mon, Feb 27, 2023 at 12:10:49PM +0100, Thomas Huth wrote:
> > Hardly anybody still uses 32-bit x86 hosts today, so we should
> > start deprecating them to finally have less test efforts.
> > With regards to 32-bit KVM support in the x86 Linux kernel,
> > the developers confirmed that they do not need a recent
> > qemu-system-i386 binary here:
> >
> >   https://lore.kernel.org/kvm/Y%2ffkTs5ajFy0hP1U@google.com/
> >
> > Signed-off-by: Thomas Huth <thuth@redhat.com>
> > ---
> >   docs/about/deprecated.rst | 13 +++++++++++++
> >   1 file changed, 13 insertions(+)
> >
> > diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
> > index 15084f7bea..98517f5187 100644
> > --- a/docs/about/deprecated.rst
> > +++ b/docs/about/deprecated.rst
> > @@ -196,6 +196,19 @@ CI coverage support may bitrot away before the deprecation 
> > process
> >   completes. The little endian variants of MIPS (both 32 and 64 bit) are
> >   still a supported host architecture.
> >   
> > +32-bit x86 hosts and ``qemu-system-i386`` (since 8.0)
> > +'''''''''''''''''''''''''''''''''''''''''''''''''''''
> > +
> > +Testing 32-bit x86 host OS support takes a lot of precious time during the
> > +QEMU contiguous integration tests, and considering that most OS vendors
> > +stopped shipping 32-bit variants of their x86 OS distributions and most
> > +x86 hardware from the past >10 years is capable of 64-bit, keeping the
> > +32-bit support alive is an inadequate burden for the QEMU project. Thus
> > +QEMU will soon drop the support for 32-bit x86 host systems and the
> > +``qemu-system-i386`` binary. Use ``qemu-system-x86_64`` (which is a proper
> > +superset of ``qemu-system-i386``) on a 64-bit host machine instead.
>
> 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.

Agreed.

> 32-bit x86 hosts
> ''''''''''''''''
>
> Support for 32-bit x86 host deployments is increasingly uncommon in
> mainstream Linux distributions given the widespread availability of
> 64-bit x86 hardware. The QEMU project no longer considers 32-bit
> x86 support to be an effective use of its limited resources, and
> thus intends to discontinue it.
>
> Current users of QEMU on 32-bit x86 hosts should either continue
> using existing releases of QEMU, with the caveat that they will
> no longer get security fixes, or migrate to a 64-bit platform
> which remains capable of running 32-bit guests if needed.
Ack.

> ``qemu-system-i386`` binary removal
> '''''''''''''''''''''''''''''''''''
>
> The ``qemu-system-x86_64`` binary can be used to run 32-bit guests
> by selecting a 32-bit CPU model, including KVM support on x86_64
> hosts. Once support for the 32-bit x86 host platform is discontinued,
> the ``qemu-system-i386`` binary will be redundant.

Missing "kvm" in this last sentence?  It is otherwise untrue for tcg.


> Current users are
> recommended to reconfigure their systems to use the ``qemu-system-x86_64``
> binary.

Ack.

> Same point for the next patch about 32-bit arm vs qemu-system-arm
> binary.

Ack.


r~