As we know, a page fault exception is caused when a process is seeking to access an area of virtual memory that is not mapped to any physical memory, when a write is attempted on a read-only page, when accessing a PTE or PDE with the reserved bit.
Regards to the reserved bit case, does anyone know how the page table is built for a process and for the kernel page table? When building the page table of a process, how can the reserved bit of a PTE or a PDE is set? Is it is set by MMU or from OS?.
Thank you,
CPU can only understand virtual addresses regardless of whether it is kernel page or user page. It is the MMU that uses the PTE to convert this virtual address into a physical address.
Go through Paging for more info