Conflicting parameters on qemu call

[Daniel P. Berrangé]

On Thu, Aug 20, 2020 at 08:11:30PM +0200, Jan Walzer wrote:
> Hi Lists,
> 
> I currently have the issue of wanting to use emu-system-x86_64 on a ppc64le platform.
> 
> It is imperative to pass the "-accel tcg,thread=multi” parameter to qemu 
> when starting an instance, as without that, it will only use one thread 
> and hence of limited/no use.
>
> The problem is, that libvirt itself, passes “-machine q35,accel=tcg” to
> qemu, which is a different parameter, that conflicts with the other one.
> 
> Can we discuss, if I either have overlooked something, or is there a workaround, or is this a bug?

What you're trying todo is intentionally not available.

The memory ordering constraints needed for running x86_64 guests on ppc64
hosts cannot be satisfied, so multi-threaded TCG is not available.

For any guest/host combination where multi-thread TCG is safe to use, QEMU
will enable it automatically, so nothing is required in libvirt.

Regards,
Daniel
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