use of -mcmodel=kernel flag in x86 platform

I am trying to cross compile a device driver built for x86 architecture to arm platform. It got compiled without any errors, but I dont think whole features are available. So I checked the makefile and found this particular part.

ifeq ($(ARCH),x86_64)    EXTRA_CFLAGS += -mcmodel=kernel -mno-red-zone

This is the only part that depends on architecture it seems. After some time on google, I found that -mcmodel=kernel is for kernel code model and -mno-red-zone is to avoid using red zone in memory and both them were for x86_64. But its not clear to me, what impact does it make setting cmodel to kernel?

(Any insight into the problem with arm is also greatly appreciated.)