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

[Krish Sadhukhan <krish.sadhukhan@oracle.com>]

On 05/13/2019 11:49 AM, Sean Christopherson wrote:
> 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.

I will combine the exposure of the control and its backing functionality 
into a single patch. But I would prefer to keep the consistency checks 
in separate patches just to make it a gradual progression i.e., first 
enabling the controls in a  patch and then checking their consistency in 
the successive patch.

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