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

[Paolo Bonzini <pbonzini@redhat.com>]

Il 09/10/2013 18:35, Gleb Natapov ha scritto:
> 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.

Yes.  I would also like to include the PPC patches that Alex pointed to
us, but I need a Tested-by because the backport isn't trivial.

If it doesn't come soon (i.e. by friday), I'll drop them and include
only your patch.

Paolo