Messages in this thread | | | Date | Fri, 26 Jan 2018 09:59:01 -0800 | From | Andi Kleen <> | Subject | Re: [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation |
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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@infradead.org> 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
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