Re: [PATCH] KVM: nVMX: fix shadow on EPT

[Gleb Natapov <gleb@redhat.com>]

On Wed, Oct 09, 2013 at 06:19:52PM +0200, Paolo Bonzini wrote:
> Il 09/10/2013 18:13, Gleb Natapov ha scritto:
> > 72f857950f6f19 broke shadow on EPT. This patch reverts it and fixes PAE
> > on nEPT (which reverted commit fixed) in other way.
> > 
> > Shadow on EPT is now broken because while L1 builds shadow page table
> > for L2 (which is PAE while L2 is in real mode) it never loads L2's
> > GUEST_PDPTR[0-3].  They do not need to be loaded because without nested
> > virtualization HW does this during guest entry if EPT is disabled,
> > but in our case L0 emulates L2's vmentry while EPT is enables, so we
> > cannot rely on vmcs12->guest_pdptr[0-3] to contain up-to-date values
> > and need to re-read PDPTEs from L2 memory. This is what kvm_set_cr3()
> > is doing, but by clearing cache bits during L2 vmentry we drop values
> > that kvm_set_cr3() read from memory.
> > 
> > So why the same code does not work for PAE on nEPT? kvm_set_cr3()
> > reads pdptes into vcpu->arch.walk_mmu->pdptrs[]. walk_mmu points to
> > vcpu->arch.nested_mmu while nested guest is running, but ept_load_pdptrs()
> > uses vcpu->arch.mmu which contain incorrect values. Fix that by using
> > walk_mmu in ept_(load|save)_pdptrs.
> > 
> > Signed-off-by: Gleb Natapov <gleb@redhat.com>
> 
> The new fix also looks much more obvious.
> 
> Applied to queue, thanks.
> 
The patch that break shadow on EPT is in master IIRC, if it is the case
consider this for -rc5.

--
			Gleb.