On Wed, Jan 20, 2021 at 10:17:36AM +0000, David Edmondson wrote: > On Wednesday, 2021-01-20 at 10:08:03 GMT, Daniel P. Berrangé wrote: > > > On Tue, Jan 19, 2021 at 11:30:52AM -0500, Eduardo Habkost wrote: > >> On Tue, Jan 19, 2021 at 04:27:56PM +0000, David Edmondson wrote: > >> > On Tuesday, 2021-01-19 at 10:20:56 -05, Eduardo Habkost wrote: > >> > > >> > > Hi, > >> > > > >> > > Thanks for the patch. Getting rid of special -feature/+feature > >> > > behavior was in our TODO list for a long time. > >> > > > >> > > On Tue, Jan 19, 2021 at 02:22:06PM +0000, David Edmondson wrote: > >> > >> "Minus" features are applied after "plus" features, so ensure that a > >> > >> later "plus" feature causes an earlier "minus" feature to be removed. > >> > >> > >> > >> This has no effect on the existing "-feature,feature=on" backward > >> > >> compatibility code (which warns and turns the feature off). > >> > > > >> > > If we are changing behavior, why not change behavior of > >> > > "-feature,feature=on" at the same time? This would allow us to > >> > > get rid of plus_features/minus_features completely and just make > >> > > +feature/-feature synonyms to feature=on/feature=off. > >> > > >> > Okay, I'll do that. > >> > > >> > Given that there have been warnings associated with > >> > "-feature,feature=on" for a while, changing that behaviour seems > >> > acceptable. > >> > > >> > Would the same be true for changing "-feature,+feature"? (i.e. what this > >> > patch does) Really: can this just be changed, or does there have to be > >> > some period where the behaviour stays the same with a warning? > >> > >> I actually expected warnings to be triggered when using > >> "-feature,+feature" as well. If we were not generating warnings > >> for that case, it will need more careful evaluation, just to be > >> sure it's safe. Igor, do you remember the details here? > > > > Where are you expecting warnings ? I don't see any when launching QEMU > > qemu-system-x86_64 -display none -cpu Westmere,-vmx,+vmx > > Warnings because the result of this is "-vmx". > > > IMHO just leave the parsing unchanged, deprecate it, and then delete > > the code. We don't need to "improve" usability semantics of something > > that we want to delete anyway. > > /me nods.
I agree, but I guess we need to convince Paolo: https://lore.kernel.org/qemu-devel/1990888058.22417362.1465939000140.javamail.zim...@redhat.com/ -- Eduardo
