Re: [PATCH v6 2/3] KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL

[Paolo Bonzini]

On 21/06/19 07:57, Tao Xu wrote:
> +	if (guest_cpuid_has(vcpu, X86_FEATURE_WAITPKG))
> +		atomic_switch_umwait_control_msr(vmx);
> +

guest_cpuid_has is slow.  Please replace it with a test on
secondary_exec_controls_get(vmx).

Are you going to look into nested virtualization support?  This should
include only 1) allowing setting the enable bit in secondary execution
controls, and passing it through in prepare_vmcs02_early; 2) reflecting
the vmexit in nested_vmx_exit_reflected.

Thanks,

Paolo