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

[Paolo Bonzini]

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.

Paolo