Re: [PATCH v2 0/3] target/i386: allow using named CPU modeles with user mode emulation

[Richard Henderson <richard.henderson@linaro.org>]

On 6/26/23 11:37, Paolo Bonzini wrote:
> On Mon, Jun 26, 2023 at 11:36 AM Daniel P. Berrangé <berrange@redhat.com> wrote:
>>>> If someone wants Nehalem then they should be using qemu-x86_64.
>>>> If someone wants qemu-i386 then they should be using an older
>>>> named CPU model predating 'lm'.
>>>
>>> What you write is true for qemu-system-*, but the problem is that
>>> qemu-user binaries are only able to run one ELF target. qemu-x86_64 is
>>> not able to run i386 binaries, unlike a 64-bit kernel; and that's
>>> really intrinsic in the design of qemu-user because implementing
>>> multiple ABIs (including multiple definitions of structs and syscall
>>> numbers) would require compiling the same files multiple times.
>>
>> Oh, right, yes, ignore my comment.
> 
> By the way it's possible that the above comment would not be true
> anymore with the "one binary" work that is going on (though I'm not
> sure if that applies to system emulation only). However, the effect on
> speed for 32-bit hosts remains true until we ditch them altogether.

Yes, one binary work is system-mode only.
Primarily because of the ABI issues you describe.


r~