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

[Gleb Natapov <gleb@redhat.com>]

On Tue, Aug 06, 2013 at 01:31:03PM +0300, Gleb Natapov wrote:
> On Tue, Aug 06, 2013 at 12:25:55PM +0200, Jan Kiszka wrote:
> > On 2013-08-06 12:12, Gleb Natapov wrote:
> > > On Tue, Aug 06, 2013 at 10:39:59AM +0200, Jan Kiszka wrote:
> > >> From: Jan Kiszka <jan.kiszka@siemens.com>
> > >>
> > >> If nested EPT is enabled, the L2 guest may change CR3 without any exits.
> > >> We therefore have to read the current value from the VMCS when switching
> > >> to L1. However, if paging wasn't enabled, L0 tracks L2's CR3, and
> > >> GUEST_CR3 rather contains the real-mode identity map. So we need to
> > >> retrieve CR3 from the architectural state after conditionally updating
> > >> it - and this is what kvm_read_cr3 does.
> > >>
> > > I have a headache from trying to think about it already, but shouldn't
> > > L1 be the one who setups identity map for L2? I traced what
> > > vmcs_read64(GUEST_CR3)/kvm_read_cr3(vcpu) return here and do not see
> > > different values in real mode.
> > 
> > Did you try with my patches applied and unrestricted guest mode in use?
> > 
> No, for that I need to setup nested environment on the machine that
> support unrestricted guest first :)
> 
Did that. I see unrestricted guest is enabled in L1, but still do not
see different values.

--
			Gleb.