Re: [Qemu-devel] [PATCH] Replace '-machine accel=xyz' with '-accel xyz'

[Paolo Bonzini <pbonzini@redhat.com>]

On 23/09/19 13:30, Markus Armbruster wrote:
> -accel is yet another convenience option.  We have so many of them.  I
> dislike the complexity they add to the CLI.  Here's how this one got in:
> 
> commit 8d4e9146b3568022ea5730d92841345d41275d66
> Author: KONRAD Frederic <fred.konrad@greensocs.com>
> Date:   Thu Feb 23 18:29:08 2017 +0000
> 
>     tcg: add options for enabling MTTCG
>     
>     We know there will be cases where MTTCG won't work until additional work
>     is done in the front/back ends to support. It will however be useful to
>     be able to turn it on.
>     
>     As a result MTTCG will default to off unless the combination is
>     supported. However the user can turn it on for the sake of testing.
>     
>     Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
>     [AJB: move to -accel tcg,thread=multi|single, defaults]
>     Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>     Reviewed-by: Richard Henderson <rth@twiddle.net>
> 
> Not a peep on why the existing options are so insufficient we must have
> another one.
> 
> Our CLI will remain the steaming mess it has become until we reform the
> habits that got us there.

-accel's accel suboption is currently defined as a convenience option,
but it shouldn't be.  It's the older "-M accel=foo:bar" that should
become "-accel foo -accel bar" and -accel then is the preferred way.

The existing option "-M accel" was insufficient because it didn't allow
accelerator-specific suboptions; they were all over the place ("-machine
kernel_irqchip", "-tb-size", etc.) and indeed mostly in wrong places.

Paolo