Re: dropping 32-bit host support

[Philippe Mathieu-Daudé]

On 16/3/23 08:17, Andrew Randrianasulu wrote:
> чт, 16 мар. 2023 г., 10:05 Philippe Mathieu-Daudé <philmd@linaro.org 
> <mailto:philmd@linaro.org>>:
>
>     Hi Andrew,
>
>     On 16/3/23 01:57, Andrew Randrianasulu wrote:
>      > Looking at https://wiki.qemu.org/ChangeLog/8.0
>     <https://wiki.qemu.org/ChangeLog/8.0>
>      > <https://wiki.qemu.org/ChangeLog/8.0
>     <https://wiki.qemu.org/ChangeLog/8.0>>
>      >
>      > ===
>      > System emulation on 32-bit x86 and ARM hosts has been deprecated.
>     The
>      > QEMU project no longer considers 32-bit x86 and ARM support for
>     system
>      > emulation to be an effective use of its limited resources, and thus
>      > intends to discontinue.
>      >
>      >   ==
>      >
>      > well, I guess arguing from memory-consuption point on 32 bit x86
>     hosts
>      > (like my machine where I run 32 bit userspace on 64 bit kernel)
>     is not
>
>     If you use a 64-bit kernel, then your host is 64-bit :)
>
>
>
> No, I mean *kernel* is 64 bit yet userspace (glibc, X , ...) all 32bit. 
> So, qemu naturally will be 32-bit binary on my system.

This configuration is still supported!

Thomas, should we clarify yet again? Maybe adding examples?

>     host: hardware where you run QEMU
>     guest: what is run within QEMU
>
>     Running 32-bit *guest* on your 64-bit *host* is still supported.
>
>     We don't plan to support running 32-bit WinXP x86 (guest) on 32-bit
>     Raspberry Pi 2 (host) for example.
>
>      > going anywhere, but what about 32bit userspace on Android tablets,
>      > either via Limbo emulator or qemu itself in Termux?
>
>     *System* emulation [on 32-bit hosts] is deprecated. User emulation
>     (such linux-user) is not. For example, you can still run 64-bit x86_64
>     Linux binaries on a 32-bit ARM Raspberry Pi.
>
>
>
> Well, unrooted Android does not allow you to just load some perfectly 
> fine kernel module, so user-space emulation can't do all things 
> system-level one can. I also ran qemu-system-ppc on Huawei Matepad T8 
> (32 bit Android, too) for emulating old mac os 9. Yes, I can wait 10 min 
> per guest boot. Fedora 36 armhf boots even slower on emulation!

Huawei MatePad T8 is based on a MediaTek MT8768 CPU which contains
ARM Cortex-A53 cores. These cores implements the ARMv8-A 64-bit ISA,
so theoretically it is able to run a 64-bit Android.

>      > At least I hope it will be not *actively* (intentionally) broken,
>     just
>      > ...unsupported (so users who know how to run git revert still
>     will get
>      > their build for some more time).
>
>     Unsupported code almost always unintentionally end bit-rotting...
>
>
>
> Well, sometimes simple patch restores functionality. I patched for 
> example olive-editor to run on 32 bit, and before this intel embree 
> (raytracing kernels for Lux renderer). So, _sometimes_ it really not 
> that costly. While if this CI thing really runs per-commit and thrown 
> away each result ... may be letting interested users to build things on 
> their own machines (and share patches, if they develop them, publicly)  
> actually good idea.
>
>
>
>     I hope this is clearer.
>
>     Regards,
>
>     Phil.