From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [RFC PATCH 3/4] mmu: don't set the present bit unconditionally
Date: Wed, 22 Jun 2016 18:12:01 +0200
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 <jpglh1x9pck.fsf@linux.bootlegged.copy>
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Cc: kvm@vger.kernel.org, guangrong.xiao@linux.intel.com
To: Bandan Das <bsd@redhat.com>
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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;

Paolo