KVM: x86: work around infinite loop in microcode when #AC is delivered

It was found that a guest can DoS a host by triggering an infinite
stream of "alignment check" (#AC) exceptions.  This causes the
microcode to enter an infinite loop where the core never receives
another interrupt.  The host kernel panics pretty quickly due to the
effects (CVE-2015-5307).

Signed-off-by: Eric Northup <digitaleric@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
static void hardware_disable(void)
{
	if (vmm_exclusive) {
		vmclear_local_loaded_vmcss();
		kvm_cpu_vmxoff();
	}
	cr4_clear_bits(X86_CR4_VMXE);
}

static void hardware_disable(void)
{
	if (vmm_exclusive) {
		vmclear_local_loaded_vmcss();
		kvm_cpu_vmxoff();
	}
	cr4_clear_bits(X86_CR4_VMXE);
}
