On Mon, Mar 4, 2013 at 8:45 PM, Nakajima, Jun <jun.nakajima@xxxxxxxxx> wrote:
> I have some updates on this. We rebased the patched to the latest KVM
> (L0). It turned out that the version of L1 KVM/Linux matters. At that
> time, actually I used v3.7 kernel for L1, and the L2 didn't work as I
> described above. If I use v3.5 or older for L1, L2 works with the EPT
> patches. So, I guess some changes made to v3.6 might have exposed a
> bug with the nested EPT patches or somewhere. We are looking at the
> changes to root-cause it.
>
Finally I've had more time to work on this, and I think I've fixed
this. The problem was that the exit qualification for EPT violation
(to L1) was not accurate (enough). And I needed to save the exit
qualification upon EPT violation somewhere. Today, that information is
converted to error_code (see below), and we lose the information. We
need to use at least the lower 3 bits when injecting EPT violation to
the L1 VMM. I tried to use the upper bytes of error_code to pass part
of the exit qualification, but it didn't work well. Any suggestion for
the place to store the value? kvm_vcpu?
...
/* It is a write fault? */
error_code = exit_qualification & (1U << 1);
/* ept page table is present? */
error_code |= (exit_qualification >> 3) & 0x1;
return kvm_mmu_page_fault(vcpu, gpa, error_code, NULL, 0);
--
Jun
Intel Open Source Technology Center
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