On Wed, May 15, 2019 at 12:09:04PM +0100, Dr. David Alan Gilbert wrote: > * Dave Martin (dave.mar...@arm.com) wrote: > > On Wed, May 15, 2019 at 09:18:54AM +0100, Andrew Jones wrote: > > > On Tue, May 14, 2019 at 04:48:38PM +0200, Igor Mammedov wrote: > > > > On Tue, 14 May 2019 11:02:25 +0200 > > > > Andrew Jones <drjo...@redhat.com> wrote: > > > > > My thought is primarily machines. If a human wants to use the command > > > > > line and SVE, then I'm assuming they'll be happy with sve-max-vq or > > > > > figuring out a map they like once and then sticking to it. > > > > > > > > maybe naive question, but why not use a property/bit as user facing > > > > interface, > > > > in line with what we do with CPUID bits. (that's assuming that bits have > > > > fixed meaning). > > > > Yes, it's verbose but follows current practice and works fine with -cpu > > > > and > > > > -device. > > > > (I really hate custom preprocessing of -cpu and we were working hard to > > > > remove > > > > that in favor of canonical properties at the expense of more verbose > > > > CLI). > > > > > > > > > > Are you asking if we should do something like the following? > > > > > > -cpu host,sve1=on,sve=2=on,sve3=off,sve4=on > > > > Note, there is nothing SVE-specific about this. > > > > Either enabling features on a per-vcpu basis is justified, or it isn't: > > if it's justified, then it would be better to have a general way of > > specifying per-vcpu properties, rather than it being reinvented per > > feature. > > SVE *is* a bit unusual. In most CPU features they're actually features, > they're on or off, so we have a big list of features that are > enabled/disabled. We've had that type of thing (at least on x86) for > years and it's OK. > We've got one or two things where they're numerical > (e.g. host-physbits) and we struggle a bit with how to handle them. > > SVE is somewhere in between - it's a list of numbers, apparently a > fairly large arbitrarily set of numbers that could be chosen so you'd > need lots of feature flags (sve1...sve64 say or more); so that doesn't > fit the existing things we've had that have worked.
I see what you mean now. SVE configuration is indeed more than just a boolean flag. Cheers ---Dave
