Re: [RFC v12 00/65] arm cleanup experiment for kvm-only build

[Claudio Fontana]

On 3/28/21 9:27 PM, Richard Henderson wrote:
> On 3/26/21 1:35 PM, Claudio Fontana wrote:
>> Here a new version of the series that enables kvm-only builds.
>>
>> The goal here is to enable the KVM-only build, but there is
>> some additional cleanup too.
>>
>> In this iteration I mostly fixed existing issues, and added an attempt
>> to put more content in cpu-sve. More splitting still required
>> for both cpu-sve and cpu-auth.
>>
>> Comments welcome, thanks,
> 
> My number 1 takeaway is that I don't think we should bother trying so hard to 
> compile out aarch64-specific code.  The number of ifdefs seems to be quite 
> high 
> in the end.
> 

Understand - it turns out to be useful in practice though to go through some 
effort
to improve the distinction between aarch64-specific code , aarch32-specific 
code,
and code that is common to both, even though we might later decide to just have 
basically TARGET_AARCH64 be always true (ie removing it)
in a future series.

> The cleanup that I think would be better would be to *remove* the 32-bit-only 
> qemu-system-arm and build it all into a single binary.  That would reduce the 
> number of build combinations and could in turn simplify or speed up CI.

Still, I think it is interesting for the reader of the code, and in trying to 
debug issues,
to be mindful about which code is 32bit-only, which code is 64-bit only, which 
is common.

Not that this series fixes everything in this regard.

> 
> We probably cannot remove qemu-arm for 32-bit linux-user binaries.  But my 
> guess is the amount of aarch64-specific code that would leak in is pretty 
> minimal.  The bulk of the difference is in the set of tcg helpers, which are 
> segregated already.
> 
> The tcg/kvm split is much more interesting, and that part of the patch set 
> looks pretty good.
> 
> 
> r~
> 

Thanks, I'll send a new version momentarily, we can continue from there.

Ciao,

Claudio