arch, hypervisor, vmm: Patch CPUID subleaves to expose EPC sections

The support for SGX is exposed to the guest through CPUID 0x12. KVM
passes static subleaves 0 and 1 from the host to the guest, without
needing any modification from the VMM itself.

But SGX also relies on dynamic subleaves 2 through N, used for
describing each EPC section. This is not handled by KVM, which means
the VMM is in charge of setting each subleaf starting from index 2
up to index N, depending on the number of EPC sections.

These subleaves 2 through N are not listed as part of the supported
CPUID entries from KVM. But it's important to set them as long as index
0 and 1 are present and indicate that SGX is supported.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

Cargo.lock

@@ -65,6 +65,7 @@ dependencies = [
  "kvm-ioctls",
  "libc",
  "linux-loader",
+ "log 0.4.8",
  "rand 0.7.3",
  "vm-memory",
 ]