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Re: [Qemu-devel] [PATCH] accel: Improve selection of the default acceler
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator |
Date: |
Tue, 9 Oct 2018 15:43:12 +0200 |
On Tue, 09 Oct 2018 15:14:59 +0200
Markus Armbruster <address@hidden> wrote:
> Markus Armbruster <address@hidden> writes:
>
> > Peter Maydell <address@hidden> writes:
> >
> >> On 5 October 2018 at 15:13, Thomas Huth <address@hidden> wrote:
> >>> When compiling with "--disable-tcg", we currently still use "tcg"
> >>> as default accelerator. "kvm" should be used in this case instead.
> >>
> >> This part is non-controversial and makes good sense.
> >
> > Agreed.
> >
> >>> Also, some downstream distros provide QEMU binaries which have "kvm"
> >>> in their names (e.g. "qemu-kvm" on RHEL or "kvm" on Ubuntu) that use
> >>> KVM by default - and some users might want to do something similar
> >>> with upstream binaries, too. Accomodate them by using "kvm:tcg" as
> >>> default when we detect such a binary name.
> >>
> >> This part is much riskier and less clearly a good plan --
> >> do we really want our behaviour to vary based on the name
> >> of the executable? Distros who want that sort of qemu-kvm
> >> wrapper generally are providing it already (the Ubuntu one
> >> is a 2-line shell script).
> >
> > I hate it when argv[0] affects behavior[*]. I hate shell wrappers less.
> >
> > If a system provides just one qemu executable, and its default
> > accelerator should be something other than tcg:kvm, then there's a use
>
> Correction: "other than tcg". See configure_accelerator().
>
> Remind me, why is "tcg" a good default?
I'm not sure why a single accelerator (any of them) would be a good
default. A list (tcg:kvm:<whatever>) sounds much saner, as it would
continue to work even if some accelerators have been disabled (right?)
(And I'd prefer kvm to be first in that list; anything that relies on
tcg being used should specify it explicitly... a normal user will
likely always want the fast variant.)
>
> > for making it compile-time configurable. Reading the default from /etc/
> > would also work. Not sure such a system exists.
Or making it overrideable like that.
> >
> >
> >
> > [*] Go document the behavior with proper precision, and you might come
> > to share the feeling.
>
- [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator, Thomas Huth, 2018/10/05
- Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator, Cornelia Huck, 2018/10/05
- Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator, Peter Maydell, 2018/10/05
- Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator, Paolo Bonzini, 2018/10/05
- Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator, Markus Armbruster, 2018/10/09
- Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator, Markus Armbruster, 2018/10/09
- Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator, Thomas Huth, 2018/10/09
- Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator, Daniel P . Berrangé, 2018/10/09
- Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator,
Cornelia Huck <=
- Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator, Peter Maydell, 2018/10/09
- Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator, Daniel P . Berrangé, 2018/10/09
- Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator, Peter Maydell, 2018/10/09
- Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator, Cornelia Huck, 2018/10/09
- Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator, Paolo Bonzini, 2018/10/09
Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator, Philippe Mathieu-Daudé, 2018/10/05