On Tue, 2018-02-06 at 21:25 +0100, Peter Krempa wrote:
On Tue, Feb 06, 2018 at 17:54:55 +0100, Andrea Bolognani wrote:
Applies on top of [req].
RFC because we still don't have a way of probing QEMU to figure out whether the relevant toggles are available. Plus, there's no documentation yet :)
I wanted to moan about missing docs and sub-par commit messages but okay. Note that without documentation it's not possible to scrunitize whether it makes any particular sense to expose a given feature at all.
See https://bugzilla.redhat.com/show_bug.cgi?id=1525599#c4 for a rationale on having the toggles. The previous comment lists all QEMU-level toggles, and as you can see we're not implementing either VSX or DFP because they don't have a clear use case.
Since probing is not implemented I don't think it makes sense to introduce cabapility bits for every single feature since they are grouped under the same version check.
Even if qemu adds QMP probing of these the capability check will not go away since it would create a regression in behaviour. This means that you can remove all the capability bits and group all of them under a single one since they will only ever be enabled using that version check.
The capabilities have been introduced during the 2.12 development cycle, so assuming QMP probing makes it into that release we should definitely use that instead of performing a version check. If it doesn't then yeah, a version check will probably be better in order not to artificially block perfectly good QEMU binaries from using the capabilites. It would still not be a regression, though.
Also I really don't think that every single feature should have it's own XML document to test it. You can gradually add them to a single one and test that all are added.
Good point, I'll merge them. -- Andrea Bolognani / Red Hat / Virtualization