How to change page permission from inside the kernel?

I have a memory page allocated with mmap() from user space, This address is passed to some kernel module (kvm_intel to be specific) and i want to know how can I change the page permission from inside there My goal is to achieve something like this mprotect(mem, PAGE_SIZE, PROT_READ) except for mprotect can't be called from the kernel, and I couldn't find the right way to do it.