Re: [RFC PATCH] configure: deprecate 32 bit build hosts

[Thomas Huth <thuth@redhat.com>]

On 26/09/2019 15.46, Christian Borntraeger wrote:
> 
> 
> On 26.09.19 14:58, Daniel P. Berrangé wrote:
>> On Thu, Sep 26, 2019 at 08:50:36AM +0100, Peter Maydell wrote:
>>> On Thu, 26 Sep 2019 at 00:31, Alex Bennée <alex.bennee@linaro.org> wrote:
>>>>
>>>> The 32 bit hosts are already a second class citizen especially with
>>>> support for running 64 bit guests under TCG. We are also limited by
>>>> testing as actual working 32 bit machines are getting quite rare in
>>>> developers personal menageries. For TCG supporting newer types like
>>>> Int128 is a lot harder with 32 bit calling conventions compared to
>>>> their larger bit sized cousins. Fundamentally address space is the
>>>> most useful thing for the translator to have even for a 32 bit guest a
>>>> 32 bit host is quite constrained.
>>>>
>>>> As far as I'm aware 32 bit KVM users are even less numerous. Even
>>>> ILP32 doesn't make much sense given the address space QEMU needs to
>>>> manage.
>>>
>>> For KVM we should wait until the kernel chooses to drop support,
>>> I think.
>>
>> What if the kernel is waiting for QEMU to drop support too ;-P
> 
> For what its worth on kvm/s390 we never cared about implementing
> 32 bit. 

Looking at tcg/s390/tcg-target.inc.c :

...
/* We only support generating code for 64-bit mode.  */
#if TCG_TARGET_REG_BITS != 64
#error "unsupported code generation mode"
#endif
...

... it seems to me that TCG does not support 32-bit on s390 either. I
think we can remove s390 (32-bit) from the list completely?

 Thomas