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Re: [Qemu-devel] [PATCH 1/2] accel: allows to select the "best" accelera
From: |
Thomas Huth |
Subject: |
Re: [Qemu-devel] [PATCH 1/2] accel: allows to select the "best" accelerator |
Date: |
Tue, 4 Oct 2016 14:49:21 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 |
On 04.10.2016 14:41, Paolo Bonzini wrote:
>
>
> On 04/10/2016 13:30, Laurent Vivier wrote:
>> But sometime, user wants to use a real accelerator without knowing
>> if he really can, with, for instance accel=kvm:tcg.
>> In this case, and if the accelerator is not available we
>> have a noisy "XXX accelerator not found".
>>
>> By allowing the user to ask the "best" accelerator for the given
>> target, we can avoid this problem.
>>
>> This patch introduces a new parameter for the "accel" property, the
>> "best" keyword.
>>
>> You can ask to use the best accelerator with "-M accel=best",
>> or if you want to use your favorite accelerator and if it is not
>> available, the best one, you can use, for instance
>> "-M accel=kvm:best".
>
> I don't think there's a single definition of a "best" accelerator. For
> example, some "-cpu" features may be available only with TCG. In that
> case, "kvm:tcg" has a clear meaning ("kvm" if it exists, otherwise
> "tcg") but "best" doesn't.
>
> I agree with Daniel that unit tests should use "tcg" exclusively, at
> least as a default.
Using only tcg has also some disadvantages: For some tests, it's
interesting to know whether they also work properly with KVM (e.g.
migration tests), and only using tcg by default slows down the "make
check" quite a bit - which might become an issue now that we're adding
more and more tests.
So maybe we need something like a qtest_get_accel() function that
returns "tcg" by default, but if the user set an environment variable
like QTEST_ACCEL, it uses that value instead?
Thomas
- [Qemu-devel] [PATCH 0/2] introduce "accel=best", Laurent Vivier, 2016/10/04
- [Qemu-devel] [PATCH 1/2] accel: allows to select the "best" accelerator, Laurent Vivier, 2016/10/04
- Re: [Qemu-devel] [PATCH 1/2] accel: allows to select the "best" accelerator, Daniel P. Berrange, 2016/10/04
- Re: [Qemu-devel] [PATCH 1/2] accel: allows to select the "best" accelerator, Paolo Bonzini, 2016/10/04
- Re: [Qemu-devel] [PATCH 1/2] accel: allows to select the "best" accelerator,
Thomas Huth <=
- Re: [Qemu-devel] [PATCH 1/2] accel: allows to select the "best" accelerator, Daniel P. Berrange, 2016/10/04
- Re: [Qemu-devel] [PATCH 1/2] accel: allows to select the "best" accelerator, Thomas Huth, 2016/10/04
- Re: [Qemu-devel] [PATCH 1/2] accel: allows to select the "best" accelerator, Paolo Bonzini, 2016/10/04
- Re: [Qemu-devel] [PATCH 1/2] accel: allows to select the "best" accelerator, Michael S. Tsirkin, 2016/10/04
- Re: [Qemu-devel] [PATCH 1/2] accel: allows to select the "best" accelerator, Paolo Bonzini, 2016/10/05
- Re: [Qemu-devel] [PATCH 1/2] accel: allows to select the "best" accelerator, Thomas Huth, 2016/10/05
- Re: [Qemu-devel] [PATCH 1/2] accel: allows to select the "best" accelerator, Paolo Bonzini, 2016/10/05
[Qemu-devel] [PATCH 2/2] tests: use accel=best instead of accel=kvm:tcg, Laurent Vivier, 2016/10/04
Re: [Qemu-devel] [PATCH 0/2] introduce "accel=best", Laurent Vivier, 2016/10/04