On Wed, Oct 21, 2020 at 7:57 AM Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> wrote: > > Wanpeng Li <kernellwp@xxxxxxxxx> writes: > > > On Wed, 21 Oct 2020 at 14:47, Jim Mattson <jmattson@xxxxxxxxxx> wrote: > >> > >> Per the KVM_GET_SUPPORTED_CPUID ioctl, the KVM_HINTS_REALTIME CPUID > >> bit is never supported. > >> > >> Is this just an oversight? > > > > It is a performance hint, not a PV feature and doesn't depend on KVM. > > > > True, but personally I'd prefer it to be reported in > KVM_GET_SUPPORTED_CPUID too, that would mean that userspace is in its > right to set it, just like any other PV 'thingy', even if just for > consistency. I agree. The documentation says: This ioctl returns x86 cpuid features which are supported by both the hardware and kvm in its default configuration. If the bit isn't set, then it is not supported, and a well-behaved userspace will not set it. Now, if the bit were in a completely different CPUID leaf (not a KVM-defined leaf), then one could argue that it falls outside of the realm of KVM_GET_SUPPORTED_CPUID. But it isn't, is it?
