Re: [Qemu-devel] Drop support for 32bit hosts in qemu? (was: [PULL 1/6] audio/hda: create millisecond timers that handle IO)

[Philippe Mathieu-Daudé]

On 06/27/2018 06:09 AM, Thomas Huth wrote:
> On 27.06.2018 10:52, Gerd Hoffmann wrote:
>>   Hi,
>>
>>>> Is QEMU still useful on 32-bit hosts?  Honest question!
>>>
>>> I guess it depends on what 32-bit hosts you consider. If you look at only
>>> x86 vs. x86_64 then probably x86 is not that important any more but for some
>>> embedded systems/SoCs 32bit might still be common and QEMU useful for those
>>> (also as host not only emulated).
>>
>> Well.  I've used kvm with an 32bit arm soc (cubietruck).  It's very
>> slow.  And all the arm architecture improvements to support kvm better
>> are for aarch64 only.
>>
>>> Another option might be to not support audio/hda on 32bit hosts. It's not
>>> nice either but a lot nicer than dropping support for 32bit hosts
>>> alltogether to fix a problem in device emulation.
>>
>> But it also is not useful and a waste of resources to maintain 32bit
>> host compatibility if nobody actually uses that ...
>>
>> For me testbuilds are the only reason to compile qemu for 32bit hosts.
>> Since years.
> 
> Well, while that's true for you, me and likely most of us developers,
> you can not know whether this is also true for all users of qemu. Thus
> this needs to be announced first for a couple of releases so that people
> have a chance to speak up whether they still need this or not. As
> mentioned earlier, embedded devices are often still 32-bit and I know
> that there really are people who use QEMU on embedded devices.
> 
> But I think we could at least announce now already that we intend to
> drop support for 32-bit hosts in the future (maybe not in 2 releases
> already, but, let's say in 2020? 2020 is already the EOL of Python 2, so
> that will rule out a bunch of other legacy hosts, too).

linux-user is certainly widely used on ARMv6 / ARMv7.

Known user cases:

- run ARMv7 binaries on ARMv6
- run armhf binaries on armel
- run x86-64 binaries on ARMv7