This is the 5th video in our virtual memory series. In the previous video, we learned about the page table and how the hardware performs a page table walk to do address translation. But merely finding the physical frame address in the page table is not sufficient for the hardware to do a memory access. It also needs to do certain additional checks to make sure that the access is valid. For example, it has to ensure that the page table mapping itself is valid (e.g., the page might have been swapped). Similarly, when doing a memory write, the hardware has to ensure that the page(s) are writable.
All these checks are done during address translation by looking up additional metadata stored against the page table entry. In this video, we cover what all these metadata bits needed by the hardware are, what their purpose is, and how they are stored in the page table.
In the next video, we will discuss demand paging. In the meantime, if you haven’t yet read the VM article, please do. And if you prefer reading it offline, get the ebook from the link below.
