On 07.05.2018 19:01, Paolo Bonzini wrote:

On 07/05/2018 18:50, Markus Armbruster wrote:

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Paolo Bonzini <pbonzini@redhat.com> writes:

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On 07/05/2018 13:56, Markus Armbruster wrote:

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Adding more and more ways to do the same stuff does not improve an interface. Interface design needs to be *opinionated*. If we decide -machine accel=tcg isn't a nice interface, by all means create a better one, but as replacement[*], not as addition.

Furthermore:

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>

I'm sorry, but this us sub-par. Yes, the commit is also about "enabling MTTCG", but it also adds a new way to select accelerators, without ever spelling that out. It should've been split, and properly described.

Perhaps we can deprecate "-M accel" then, and also while we're at it move kernel_irqchip from -machine to "-accel kvm" where it belongs?

Sounds good to me.

Thomas, here's one for you! :)

I like the idea of deprecating "-machine accel=xxx" - but that will also be a bigger change, since "-accel" is internally setting the accel option of the machine again... Also libvirt is still using "-machine accel=..." as far as I know, so we've got to make sure that this gets changed there, too... Thomas