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

[Richard Henderson <richard.henderson@linaro.org>]

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~