On Tue, 09 Oct 2018 15:14:59 +0200 Markus Armbruster <arm...@redhat.com> wrote:
> Markus Armbruster <arm...@redhat.com> writes: > > > Peter Maydell <peter.mayd...@linaro.org> writes: > > > >> On 5 October 2018 at 15:13, Thomas Huth <th...@redhat.com> 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. >
