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. dme. -- I just bite it, it's for the look I don't light it.