Re: [RFC PATCH 3/4] mmu: don't set the present bit unconditionally

[Bandan Das <bsd@redhat.com>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 22/06/2016 18:10, Bandan Das wrote:
>>>> >> +	if (!shadow_xonly_valid)
>>>> >> +		spte = PT_PRESENT_MASK;
>>>> >>  	if (!speculative)
>>>> >>  		spte |= shadow_accessed_mask;
>>>> >>  
>>>> >> @@ -2537,8 +2538,12 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
>>>> >>  	else
>>>> >>  		spte |= shadow_nx_mask;
>>>> >>  
>>>> >> -	if (pte_access & ACC_USER_MASK)
>>>> >> -		spte |= shadow_user_mask;
>>>> >> +	if (pte_access & ACC_USER_MASK) {
>>>> >> +		if (shadow_xonly_valid)
>>>> >> +			spte |= PT_PRESENT_MASK;
>>>> >> +		else
>>>> >> +			spte |= shadow_user_mask;
>>>> >> +	}
>>> >
>>> > Can you instead pass VMX_READABLE_MASK to kvm_mmu_set_mask_ptes in vmx.c?
>> So, leave spte = PT_PRESENT_MASK as is and make VMX_READABLE_MASK 1ULL if
>> execute only is supported ?
>> And then :
>> if !(pte_access & ACC_USER_MASK) {
>>        spte &= ~VMX_READABLE_MASK 
>> 
>
> No, I meant something like
>
> 	spte = 0;
> 	if (!shadow_xonly_valid)
> 		spte = PT_PRESENT_MASK;
> 	...
> 	if (pte_access & ACC_USER_MASK)
> 		spte |= shadow_user_mask;

Ok, Xiao mentioned this too. I will fix it in the next version.
Thanks for the review.

> Paolo
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html