On Fri, Jan 26, 2018 at 09:19:09AM -0800, Linus Torvalds wrote: > On Fri, Jan 26, 2018 at 1:11 AM, David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote: > > > > Do we need to look again at the fact that we've disabled the RSB- > > stuffing for SMEP? > > Absolutely. SMEP helps make people a lot less worried about things, > but it doesn't fix the "BTB only contains partial addresses" case. > > But did we do that "disable stuffing with SMEP"? I'm not seeing it. In > my tree, it's only conditional on X86_FEATURE_RETPOLINE. For Skylake we need RSB stuffing even with SMEP to avoid falling back to the BTB on underflow. It's also always needed with virtualization. -Andi
