[RFC PATCH] docs/about/deprecated: Deprecate 32-bit host systems

[Thomas Huth]

On 30/01/2023 13.01, Daniel P. Berrangé wrote:
> On Mon, Jan 30, 2023 at 11:47:02AM +0000, Peter Maydell wrote:
>> On Mon, 30 Jan 2023 at 11:44, Thomas Huth <thuth at redhat.com> wrote:
>>>
>>> Testing 32-bit host OS support takes a lot of precious time during the QEMU
>>> contiguous integration tests, and considering that many OS vendors stopped
>>> shipping 32-bit variants of their OS distributions and most hardware from
>>> the past >10 years is capable of 64-bit
>>
>> True for x86, not necessarily true for other architectures.
>> Are you proposing to deprecate x86 32-bit, or all 32-bit?
>> I'm not entirely sure about whether we're yet at a point where
>> I'd want to deprecate-and-drop 32-bit arm host support.

Even mobile phones have 64-bit processors nowadays, Rasberry PIs are 64-bit 
nowadays ... which arm hosts scenarios are still limited to 32-bit ?

Also, as far as I know, 32-bit KVM arm support has been removed from the 
Linux kernel a while ago already, so it's just about TCG now ... is there 
really still that much interest in running emulation on a non-beefy 32-bit host?

Anyway, we could add the deprecation notice now to find out if there are 
still 32-bit users out there who will then start complaining about this.

> Do we have a feeling on which aspects of 32-bit cause us the support
> burden ? The boring stuff like compiler errors from mismatched integer
> sizes is mostly quick & easy to detect simply through a cross compile.

The burden are the CI minutes of the shared CI runners. We've got quite a 
bunch of 32-bit jobs in the CI:

- cross-armel-system
- cross-armel-user
- cross-armhf-system
- cross-armhf-user
- cross-i386-system
- cross-i386-user
- cross-i386-tci
- cross-mipsel-system
- cross-mipsel-user
- cross-win32-system

If we could finally drop supporting 32-bit hosts, that would help with our 
CI minutes problem quite a lot, I think.

  Thomas