cxl: Early return from cxl_handle_fault for a shut down context

If a context is being detached and we get a translation fault for it
there is little point getting it's mm and handling the fault, so just
respond with an address error and return earlier.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

drivers/misc/cxl/fault.c

@@ -180,6 +180,12 @@ void cxl_handle_fault(struct work_struct *fault_work)
 		return;
 	}
 
+	/* Early return if the context is being / has been detached */
+	if (ctx->status == CLOSED) {
+		cxl_ack_ae(ctx);
+		return;
+	}
+
 	pr_devel("CXL BOTTOM HALF handling fault for afu pe: %i. "
 		"DSISR: %#llx DAR: %#llx\n", ctx->pe, dsisr, dar);