From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH 2/3] kvm: add SPTE_HOST_WRITEABLE flag to the shadow
	ptes.
Date: Thu, 9 Apr 2009 06:59:49 -0300
Message-ID: <20090409095949.GB31724@amt.cnet>
References: <1238457604-7637-1-git-send-email-ieidus@redhat.com> <1238457604-7637-2-git-send-email-ieidus@redhat.com> <1238457604-7637-3-git-send-email-ieidus@redhat.com>
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Cc: kvm@vger.kernel.org
To: Izik Eidus <ieidus@redhat.com>
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On Tue, Mar 31, 2009 at 03:00:03AM +0300, Izik Eidus wrote:
> this flag notify that the host physical page we are pointing to from
> the spte is write protected, and therefore we cant change its access
> to be write unless we run get_user_pages(write = 1).
> 
> (this is needed for change_pte support in kvm)
> 
> Signed-off-by: Izik Eidus <ieidus@redhat.com>

> @@ -547,6 +551,7 @@ static void FNAME(prefetch_page)(struct kvm_vcpu *vcpu,
>  static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
>  {
>  	int i, offset, nr_present;
> +        bool reset_host_protection = 1;
>  
>  	offset = nr_present = 0;
>  
> @@ -584,9 +589,14 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
>  
>  		nr_present++;
>  		pte_access = sp->role.access & FNAME(gpte_access)(vcpu, gpte);
> +		if (!(sp->spt[i] & SPTE_HOST_WRITEABLE)) {
> +			pte_access &= ~PT_WRITABLE_MASK;
> +                        reset_host_protection = 0;
> +              }

                 else
                          reset_host_protection = 1;
                
Otherwise you clear SPTE_HOST_WRITEABLE for all sptes once you find a
single one thats unset.

Also mind the tabs.