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


From: Richard Henderson
Subject: Re: [PATCH v2 0/3] target/i386: allow using named CPU modeles with user mode emulation
Date: Mon, 26 Jun 2023 12:06:03 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0

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~



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