Re: [PATCH 1/8][KVMnVMX]: Enable "load IA32_PERF_GLOBAL_CTRL" VM-exit control for nested guests

[Sean Christopherson <sean.j.christopherson@intel.com>]

On Wed, Apr 24, 2019 at 07:17:17PM -0400, Krish Sadhukhan wrote:
> Signed-off-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
> Reviewed-by: Karl Heubaum <karl.heubaum@oracle.com>
> ---
>  arch/x86/kvm/vmx/nested.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 3170e291215d..42a4deb662c6 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -5493,7 +5493,8 @@ void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps,
>  	msrs->exit_ctls_high |=
>  		VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR |
>  		VM_EXIT_LOAD_IA32_EFER | VM_EXIT_SAVE_IA32_EFER |
> -		VM_EXIT_SAVE_VMX_PREEMPTION_TIMER | VM_EXIT_ACK_INTR_ON_EXIT;
> +		VM_EXIT_SAVE_VMX_PREEMPTION_TIMER | VM_EXIT_ACK_INTR_ON_EXIT |
> +		VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;

This exposes the control to L1 but doesn't implement the backing
functionality.  The backing functionality, consistency checks and exposure
to L1 should be a single patch.  The consistency checks could be added
earlier, but I don't see much value in doing so given that the checks are
(currently) a few lines.

>  
>  	/* We support free control of debug control saving. */
>  	msrs->exit_ctls_low &= ~VM_EXIT_SAVE_DEBUG_CONTROLS;
> -- 
> 2.17.2
>