On Tue, Sep 24, 2019 at 01:31:00PM +0200, Andrew Jones wrote: > +SVE CPU Property Parsing Semantics > +---------------------------------- > + > + 1) If SVE is disabled (`sve=off`), then which SVE vector lengths > + are enabled or disabled is irrelevant to the guest, as the entire > + SVE feature is disabled and that disables all vector lengths for > + the guest. However QEMU will still track any `sve<N>` CPU > + properties provided by the user. If later an `sve=on` is provided, > + then the guest will get only the enabled lengths.
I just spoke with Andrea, who is doing the libvirt side of this, about this behavior. He suggests that we change it such that an error is generated if sve=off and there are explicitly enabled vector lengths, e.g. '-cpu max,sve=off,sve256=on' should generate an error. It would still be possible to have sve<N>=on and sve=off on the same command line, as long as the sve<N>=on is followed by sve<N>=off, like this -cpu max,sve=off,sve256=on,sve256=off,sve128=off, but I don't think we need to worry about that sort of thing. I'll add an error for the non-empty vector length map with SVE off case for v5. Thanks, drew
