kvm: x86: disable the narrow guest module parameter on unload

When the kvm_intel module unloads the module parameter
'allow_smaller_maxphyaddr' is not cleared because the backing variable is
defined in the kvm module.  As a result, if the module parameter's state
was set before kvm_intel unloads, it will also be set when it reloads.
Explicitly clear the state in vmx_exit() to prevent this from happening.

Signed-off-by: Aaron Lewis <aaronlewis@google.com>
Message-Id: <20210623203426.1891402-1-aaronlewis@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Jim Mattson <jmattson@google.com>

arch/x86/kvm/vmx/vmx.c

@@ -7925,6 +7925,8 @@ static void vmx_exit(void)
 	}
 #endif
 	vmx_cleanup_l1d_flush();
+
+	allow_smaller_maxphyaddr = false;
 }
 module_exit(vmx_exit);