Re: [RFC v1 00/38] arm cleanup experiment for kvm-only build

[Claudio Fontana]

On 3/4/21 8:24 PM, Peter Maydell wrote:
> On Thu, 4 Mar 2021 at 16:39, Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>>
>> On 3/3/21 7:54 PM, Richard Henderson wrote:
>>> On 3/3/21 10:45 AM, Claudio Fontana wrote:
>>>> It is a bit weird that qemu-system-aarch64 runs with a cortex-a15
>>>> model tbh, as cortex-a15 is not capable of aarch64.
>>>
>>> No, but qemu-system-aarch64 is capable of 32-bit emulation (because most
>>> 64-bit cpus retain 32-bit mode).  It takes no extra effort to run
>>> cortex-a15 than it does a cortex-a57.
>>
>> IIRC qemu-system-arm starts the aa64 cores in 32-bit mode, while
> 
> ...no, it simply doesn't have them at all; it only has
> the 32-bit-only cores. We only support '64-bit core that
> starts in 32-bit mode' for KVM; it would be nice to have the
> TCG support for that but nobody's ever written it.
> 
>> qemu-system-aarch64 in 64-bit (this gave me trouble because the
>> kernels for the raspi 64-bit SoCs are in 32-bit mode -- because
>> the GPU starts them in this mode).
>>
>>> I have wondered if we should have just one qemu-system-arm that does it
>>> all and drop the separate qemu-system-aarch64 -- or vice versa.  But
>>> we've had the separation around so long I'm sure someone would be confused.
>>
>> That would be great cleanup IMHO.
> 
> I figure it's not really worth the bother until/unless we ever
> some day get to the holy grail of "one binary that supports
> multiple target architectures", at which point we could have
> one qemu-system for everything...
> 
> -- PMM
> 

"one small binary, with optionally pluggable modules for multiple target 
architectures and optional features" ?

Ciao,

Claudio