Re: [libvirt] [Qemu-devel] [PATCH v3 2/2] Add configure option --enable-pc-1-0-qemu-kvm

On 22 Sep 2014, at 12:36, Michael S. Tsirkin <mst(a)redhat.com&gt; wrote: The whole point is to make it easy for distributions to make pc-1.0 do an appropriate thing for them, an appropriate thing being what their previous release(s) meant by pc-1.0. Sadly, pc-1.0 means more than one thing - on Ubuntu it really means "qemu-kvm's pc-1.0" and on other systems (and upstream) it means "qemu-git's pc-1.0". This is horrible, but it's not the fault of this patch, is simply current reality. Right now, you can't tell what pc-1.0 does anyway, as it does a different thing on Ubuntu Precise to Ubuntu Trusty (for instance). If we're going to provide compatibility to the machine type name level (which is the purpose here) then sadly we need something like this. As for 'not being able to predict', actually post this patch the situation is far clearer, as '-M ?' tells you exactly what pc-1.0 will do, by showing what it's an alias for. Agree with that, but I couldn't think of anything better. 'qemu-upstream'? 'qemu'? Sadly that is not true. For instance on Ubuntu Precise it's invoked as qemu-system-x86_64 by at least one management application known to me. I'm not quite sure why you say "legacy management applications". This applies to /any/ management application. Unless we're going to burden every management application with this problem, we need to fix it. Just as a reminder, the ./configure value defaults to off, which means there is no change in current behaviour. Only if the ./configure value is changed does it result in the behaviour of pc-1.0 changing, and that is evident from the help line. And it's possible to specify a specific variant of 1.0 (irrespective of the default) from the command line. -- Alex Bligh