Re: [PATCH] KVM: x86: allow KVM_REQ_GET_NESTED_STATE_PAGES outside guest mode for VMX

[Paolo Bonzini <pbonzini@redhat.com>]

On 25/01/21 20:16, Sean Christopherson wrote:
>>   }
>>   
>> +static bool vmx_get_nested_state_pages(struct kvm_vcpu *vcpu)
>> +{
>> +	if (!nested_get_evmcs_page(vcpu))
>> +		return false;
>> +
>> +	if (is_guest_mode(vcpu) && !nested_get_vmcs12_pages(vcpu))
>> +		return false;
> nested_get_evmcs_page() will get called twice in the common case of
> is_guest_mode() == true.  I can't tell if that will ever be fatal, but it's
> definitely weird.  Maybe this?
> 
> 	if (!is_guest_mode(vcpu))
> 		return nested_get_evmcs_page(vcpu);
> 
> 	return nested_get_vmcs12_pages(vcpu);
> 

I wouldn't say there is a common case; however the idea was to remove 
the call to nested_get_evmcs_page from nested_get_vmcs12_pages, since 
that one is only needed after KVM_GET_NESTED_STATE and not during 
VMLAUNCH/VMRESUME.

Paolo