Re: [patch 2/3] KVM: dont require read-only host ptes

[Marcelo Tosatti <mtosatti@redhat.com>]

On Tue, Oct 05, 2010 at 03:43:01PM +0200, Gleb Natapov wrote:
> > --- kvm.orig/arch/x86/kvm/mmu.c
> > +++ kvm/arch/x86/kvm/mmu.c
> > @@ -2273,6 +2273,7 @@ static int nonpaging_map(struct kvm_vcpu
> >  {
> >  	int r;
> >  	int level;
> > +	int writable;
> >  	pfn_t pfn;
> >  	unsigned long mmu_seq;
> >  
> > @@ -2289,10 +2290,10 @@ static int nonpaging_map(struct kvm_vcpu
> >  
> >  	mmu_seq = vcpu->kvm->mmu_notifier_seq;
> >  	smp_rmb();
> > -	pfn = gfn_to_pfn(vcpu->kvm, gfn);
> > +	pfn = gfn_to_pfn(vcpu->kvm, gfn, &writable);
> >  
> >  	/* mmio */
> > -	if (is_error_pfn(pfn))
> > +	if (is_error_pfn(pfn) || !writable)
> >  		return kvm_handle_bad_page(vcpu->kvm, gfn, pfn);
> >  
> >  	spin_lock(&vcpu->kvm->mmu_lock);
> > @@ -2581,6 +2582,8 @@ static int tdp_page_fault(struct kvm_vcp
> >  	pfn_t pfn;
> >  	int r;
> >  	int level;
> > +	int writable;
> > +	int write = error_code & PFERR_WRITE_MASK;
> >  	gfn_t gfn = gpa >> PAGE_SHIFT;
> >  	unsigned long mmu_seq;
> >  
> > @@ -2597,15 +2600,14 @@ static int tdp_page_fault(struct kvm_vcp
> >  
> >  	mmu_seq = vcpu->kvm->mmu_notifier_seq;
> >  	smp_rmb();
> > -	pfn = gfn_to_pfn(vcpu->kvm, gfn);
> > -	if (is_error_pfn(pfn))
> > +	pfn = gfn_to_pfn(vcpu->kvm, gfn, &writable);
> > +	if (is_error_pfn(pfn) || !writable)
> Why would we fail read only access to read only memory? Shouldn't we
> check access type here?
> 
> --
> 			Gleb.

Next patch does that.