From: Thomas Huth <thuth@redhat.com>
To: "Alex Bennée" <alex.bennee@linaro.org>, qemu-devel@nongnu.org
Cc: "Kevin Wolf" <kwolf@redhat.com>,
"Daniel P. Berrangé" <berrange@redhat.com>,
qemu-block@nongnu.org, "Markus Armbruster" <armbru@redhat.com>,
"Wainer dos Santos Moschetta" <wainersm@redhat.com>,
"Max Reitz" <mreitz@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Philippe Mathieu-Daudé" <philmd@redhat.com>
Subject: Re: Priority of -accel (was: [PATCH] tests/qemu-iotests: Update tests to recent desugarized -accel option)
Date: Wed, 8 Jan 2020 11:58:47 +0100 [thread overview]
Message-ID: <da2111ee-0644-1d7c-a111-e4209025a1d8@redhat.com> (raw)
In-Reply-To: <87d0bujkpe.fsf@linaro.org>
On 08/01/2020 11.39, Alex Bennée wrote:
>
> Thomas Huth <thuth@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
next prev parent reply other threads:[~2020-01-08 11:02 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-06 13:09 [PATCH] tests/qemu-iotests: Update tests to recent desugarized -accel option Philippe Mathieu-Daudé
2020-01-06 13:16 ` Max Reitz
2020-01-07 10:03 ` Priority of -accel (was: [PATCH] tests/qemu-iotests: Update tests to recent desugarized -accel option) Thomas Huth
2020-01-07 10:14 ` Paolo Bonzini
2020-01-07 12:18 ` Thomas Huth
2020-01-07 12:23 ` Paolo Bonzini
2020-01-07 12:54 ` Daniel P. Berrangé
2020-01-07 14:14 ` Thomas Huth
2020-01-07 14:20 ` Priority of -accel Philippe Mathieu-Daudé
2020-01-07 14:27 ` Daniel P. Berrangé
2020-01-07 14:35 ` Thomas Huth
2020-01-13 14:39 ` Markus Armbruster
2020-01-13 16:14 ` Christophe de Dinechin
2020-01-13 16:23 ` Paolo Bonzini
2020-01-07 14:26 ` Priority of -accel (was: [PATCH] tests/qemu-iotests: Update tests to recent desugarized -accel option) Daniel P. Berrangé
2020-01-08 10:39 ` Alex Bennée
2020-01-08 10:58 ` Thomas Huth [this message]
2020-01-08 12:41 ` Paolo Bonzini
2020-01-08 13:10 ` Daniel P. Berrangé
2020-01-08 13:24 ` Paolo Bonzini
2020-01-08 14:00 ` Priority of -accel Thomas Huth
2020-01-08 11:00 ` Priority of -accel (was: [PATCH] tests/qemu-iotests: Update tests to recent desugarized -accel option) Peter Maydell
2020-01-10 10:43 ` Peter Maydell
2020-01-07 12:29 ` Kevin Wolf
2020-01-07 12:34 ` Priority of -accel Philippe Mathieu-Daudé
2020-01-07 12:37 ` Philippe Mathieu-Daudé
2020-01-07 13:55 ` Priority of -accel (was: [PATCH] tests/qemu-iotests: Update tests to recent desugarized -accel option) Christophe de Dinechin
2020-01-07 14:37 ` Paolo Bonzini
2020-01-07 14:42 ` Thomas Huth
2020-01-07 17:43 ` Christophe de Dinechin
2020-01-07 17:53 ` Peter Maydell
2020-01-08 9:47 ` Kevin Wolf
2020-01-13 16:17 ` Priority of -accel Markus Armbruster
2020-01-13 16:25 ` Paolo Bonzini
2020-01-14 8:59 ` Markus Armbruster
2020-01-14 10:44 ` Paolo Bonzini
2020-01-14 17:49 ` Christophe de Dinechin
2020-01-14 17:59 ` Daniel P. Berrangé
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