On 08/01/2020 11.39, Alex Bennée wrote: > > Thomas Huth <th...@redhat.com> writes: > >> On 07/01/2020 13.54, Daniel P. Berrangé wrote: >>> On Tue, Jan 07, 2020 at 01:23:18PM +0100, Paolo Bonzini wrote: >>>> On 07/01/20 13:18, Thomas Huth wrote: >>>>> I don't think we need a separate priority parameter here. But IMHO it's >>>>> really rather common practice to prioritize the last option. So while >>>>> it might be more "self-explanatory" to a CLI newbie if the first >>>>> occurrence got the highest priority, it might be rather confusing >>>>> instead for a CLI veteran...? >>>> >>>> Prioritising the last certainly makes sense for a choose-one-only >>>> option, but I'm not sure it's the same for a choose-best option. After >>>> all it was -machine accel=kvm:tcg, not -machine accel=tcg:kvm... >>> >>> IIUC, the main use case for specifying multiple accelerators is >>> so that lazy invokations can ask for a hardware virt, but then get >>> fallback to TCG if not available. For things that should be platform >>> portabile, there's more than just kvm to consider though, as we have >>> many accelerators. Listing all possible accelerators is kind of >>> crazy though no matter what the syntax is. >>> >>> How about taking a completely different approach, inspired by the >>> -cpu arg and implement: >>> >>> -machine accel=best >> >> Something like that sounds like the best solution to me, but I'd maybe >> rather not call it "best", since the definition of "best" might depend >> on your use-case (e.g. do you want to use a CPU close to the host or >> something different which might be better emulated by TCG?). > > Indeed - you may well want to do TCG on Aarch64 if you want to test new > instructions. > >> >> What about "-accel any" or "-accel fastest" or something similar? > > "any" is just ambiguous, "fastest" is just begging for me to find a > micro-benchmark that TCG outperforms on ;-) > > "-accel default" could be considered to have vibes of Do The Right > Thing (tm) and could in time actually become so!
"-accel default" sounds like the default behavior that you'd also get if you don't use this option at all ... what about "-accel auto" to say that QEMU should pick an accelerator automatically? Thomas
