Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator

[Markus Armbruster]

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
for making it compile-time configurable.  Reading the default from /etc/
would also work.  Not sure such a system exists.



[*] Go document the behavior with proper precision, and you might come
to share the feeling.