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Re: [Xen-devel] Intermittent fatal page fault with XEN 4.3.1 (Centos 6.3 DOM0 with linux kernel 3.10.16.)

>>> On 07.11.13 at 18:02, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> While the patch does look plausible, there is still clearly an issue
> that an HVM guest with nested_virt disabled can even use the VMX
> instructions, rather than getting flat out #UD exceptions.

The real CR4.VMXE is (of course) set, and basing a decision on the
read shadow would clearly be wrong from an architectural pov (as
then this would no longer be just a read shadow).

And this isn't the problem here anyway - one problems is that the
privilege level check is done _after_ the VMX non-root mode one.
I guess they do it that way in order to allow the VMM maximum


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