Paolo Bonzini <pbonzini@xxxxxxxxxx> writes: > 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. > > (But maybe this was discussed already; if so, please point me to the > previous discussion). > Not for KVM_GET_SUPPORTED_CPUID but for KVM_GET_SUPPORTED_HV_CPUID: just copying all the bits blindly is incorrect as e.g. SYNIC needs to be enabled with KVM_CAP_HYPERV_SYNIC[2]. KVM PV features also have pre-requisites, e.g. KVM_ASYNC_PF_DELIVERY_AS_INT requires an irqchip so again copy/paste may not work. -- Vitaly
