block size of write for write-through cache of writes to sequential words, •Increases bytes since multiword writes more efficient to memory processor, among many others, uses write merging •The Sun T1 (Niagara) 2.Explain in detail the architecture support for protecting processes from each other via virtual memory (Jun 2014) (June/July 2013)(Jan 2015) Virtual Memory and Virtual Machines Slide Sources: Based on by Hennessy/Patterson. “Computer Architecture” Supplemented from various freely downloadable sources Security and Privacy in Computer Architecture and System software •Innovations through Virtual Memory •Protection from Virtual Machines •Protection requirements –Architectural –Performance Protection via Virtual Memory •Processes program –Running (state) needed to continue running it –Environment Processes from each other •Protect based virtual memory including TLB which caches page table entries –Page Segmentation and paging in 80x86 Processes share hardware without interfering with each other User Process and Kernel Process •Provide portion of Processor state: •Readable supervisor mode bit enable/disable bit –Exception protection information –Memory to transfer to supervisor mode •System call like normal subroutine to user mode –Return to limit memory access •Mechanism Memory protection Memory •Virtual on each page entry in page table –Restriction write, execute privileges –Read, OS can update page table –Only entries also have protection field –TLB in OS •Bugs to compromising security –Lead likely due to huge size of OS code –Bugs Protection via Virtual Machines Virtualization
•Increases block size of write for write-through cache of writes to sequential words, bytes since multiword writes more efficient to memory •The Sun T1 (Niagara) processor, among many others, uses write merging 2.Explain in detail the architecture support for protecting processes from each other via virtual memory (Jun 2014) (June/July 2013)(Jan 2015) Virtual Memory and Virtual Machines Slide Sources: Based on “Computer Architecture” by Hennessy/Patterson. Supplemented from various freely downloadable sources Security and Privacy •Innovations in Computer Architecture and System software •Protection through Virtual Memory •Protection from Virtual Machines –Architectural requirements –Performance Protection via Virtual Memory •Processes –Running program –Environment (state) needed to continue running it •Protect Processes from each other –Page based virtual memory including TLB which caches page table entries Segmentation and paging in 80x86 Processes share hardware without interfering with each other •Provide User Process and Kernel Process •Readable portion of Processor state: supervisor mode bit –Exception enable/disable bit –Memory protection information •System call to transfer to supervisor mode –Return like normal subroutine to user mode •Mechanism to limit memory access Memory protection •Virtual Memory –Restriction on each page entry in page table –Read, write, execute privileges –Only OS can update page table –TLB entries also have protection field •Bugs in OS –Lead to compromising security –Bugs likely due to huge size of OS code Protection via Virtual Machines Virtualization