Re: [PATCH v2 5/8] KVM: nVMX: Fix guest CR3 read-back on VM-exit

[Gleb Natapov <gleb@redhat.com>]

On Wed, Aug 07, 2013 at 03:32:37PM +0200, Paolo Bonzini wrote:
> >>>>>diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> >>>>>index 44494ed..60a3644 100644
> >>>>>--- a/arch/x86/kvm/vmx.c
> >>>>>+++ b/arch/x86/kvm/vmx.c
> >>>>>@@ -3375,8 +3375,10 @@ static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
> >>>>>  	if (enable_ept) {
> >>>>>  		eptp = construct_eptp(cr3);
> >>>>>  		vmcs_write64(EPT_POINTER, eptp);
> >>>>>-		guest_cr3 = is_paging(vcpu) ? kvm_read_cr3(vcpu) :
> >>>>>-			vcpu->kvm->arch.ept_identity_map_addr;
> >>>>>+		if (is_paging(vcpu) || is_guest_mode(vcpu))
> >>>>>+			guest_cr3 = kvm_read_cr3(vcpu) :
> >>>>>+		else
> >>>>>+			guest_cr3 = vcpu->kvm->arch.ept_identity_map_addr;
> >>>>>  		ept_load_pdptrs(vcpu);
> >>>>>  	}
> >>>>>
> >>>>That what I am thinking, will think about it some more tomorrow.
> >>>
> >>>OK, and I'll feed it into a local test.
> >>>
> >>Thought about is some more. So without nested unrestricted guest (nUG)
> >>is_paging() will always be true (since without nUG guest entry is not
> >>possible otherwise) and guest's cr3 will be used, but with nUG identity
> >>map is not used (that is why L2 still works even though wrong identity
> >>map pointer is assigned to cr3), so the code here just corrupts nested
> >>guest's cr3 for no reason and that is why you had to use kvm_read_cr3()
> >>in prepare_vmcs12() to get correct cr3 value. The patch above should be
> >>used instead of original one IMO. How is testing going?
> >
> >Yes, testing worked fine. I've queued above patch and will send it out
> >within the next round.
> 
> Just reply here with the commit message you desire and
> Signed-off-by, so I can queue it for people who wish to play with
> nEPT.
> 
I would love to have a comment there too :)

--
			Gleb.