Taming STIBP
Taming STIBP
Posted Dec 5, 2018 18:37 UTC (Wed) by raistlin (guest, #37586)In reply to: Taming STIBP by pbonzini
Parent article: Taming STIBP
Yep. Or, if one does not use retpoline, and uses IBRS instead (e.g., on future hardware where that may be faster, or as Xen does already, in some cases), that --I mean setting IBRS when entering ring 0-- prevents BTB updates done in ring 3 to affect branches in context with more privilege (like ring 0). Or so I've understood. :-D
Posted Dec 6, 2018 9:59 UTC (Thu)
by hmh (subscriber, #3838)
[Link]
While it is likely to be true for "enhanced IBRS" (the one you leave always on, and which doesn't exist quite yet), for the current crop of processors that are way too prone to leak fleeting images of a future past, IMHO it is a IBRS property better tested before being trusted to exist.
After all, it is all about ghosts, and ghosts are tricky ;-)
Taming STIBP
That's how I understood it as well, but...