PPT Slide
Virtual Memory
- To support VM, we need the following PTE field:
- present bit - if = 1, the page is present in memory & the base address field represents a valid page frame number. If = 0, the page reference is to a legal non-mapped page.
- A memory access will now cause the following possible events (algorithm on p. 459):
- Split logical address into page and offset values.
- Check PTE entry for the page and see if the protection bits allow the appropriate access. If not, raise a protection violation interrupt.
- Check PTE present bit. If 1, the frame # in the PTE is valid. Generate the physical address by combining the physical frame number and the offset. If 0, generate a page fault interrupt.