On Thu, Oct 22, 2020 at 9:37 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > On 22/10/20 18:35, Jim Mattson wrote: > > On Thu, Oct 22, 2020 at 6:02 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > >> > >> On 22/10/20 03:34, Wanpeng Li wrote: > >>> From: Wanpeng Li <wanpengli@xxxxxxxxxxx> > >>> > >>> Per KVM_GET_SUPPORTED_CPUID ioctl documentation: > >>> > >>> This ioctl returns x86 cpuid features which are supported by both the > >>> hardware and kvm in its default configuration. > >>> > >>> A well-behaved userspace should not set the bit if it is not supported. > >>> > >>> Suggested-by: Jim Mattson <jmattson@xxxxxxxxxx> > >>> Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx> > >> > >> It's common for userspace to copy all supported CPUID bits to > >> KVM_SET_CPUID2, I don't think this is the right behavior for > >> KVM_HINTS_REALTIME. > > > > That is not how the API is defined, but I'm sure you know that. :-) > > Yes, though in my defense :) KVM_HINTS_REALTIME is not a property of the > kernel, it's a property of the environment that the guest runs in. This > was the original reason to separate it from other feature bits in the > same leaf. > > Paolo > We don't actually use KVM_GET_SUPPORTED_CPUID at all today. If it's commonly being misinterpreted as you say, perhaps we should add a KVM_GET_TRUE_SUPPORTED_CPUID ioctl. Or, perhaps we can just fix this in the documentation?
