Beautiful Architecture – Xen and the Beauty of Virtualization (Chapter 7)

Interesting that this article mentions Bochs since I actually worked on a research project that used this emulator a few years ago. Overall, this article clarified several misconceptions I had about virtual machines and did a great job distinguishing between virtualization and paravirtualization. I should point out, though, that Virtual Memory was created to make programming applications easier and to make more efficient use of memory. Not necessarily to "ensure that processes cannot interfere with the data or code of other processes". A system would still need to ensure the integrity of data access in a non-Virtual Memory implementation. And just to briefly correct Chad's statement that "All the operating systems hosted by the hypervisor share the same virtual and physical memory". Though they share the same physical address, the guest OS's have their own virtual addresses and page tables. Each OS would ask the hypervisor if it could make an update in its own page table, and the hypervisor would then make sure it doesn't conflict with the physical address mapping of another OS's page table. The article quotes, "Xen must validate all updates to the page tables, and the kernel must inform the hypervisor when it wants to change any page table".