Messages in this thread | | | Subject | Re: [tip:x86/pti] x86/retpoline: Fill RSB on context switch for affected CPUs | From | David Woodhouse <> | Date | Mon, 15 Jan 2018 11:13:16 +0100 |
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On Sun, 2018-01-14 at 16:05 -0800, Andi Kleen wrote: > > + if ((!boot_cpu_has(X86_FEATURE_PTI) && > > + !boot_cpu_has(X86_FEATURE_SMEP)) || is_skylake_era()) { > > + setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW); > > + pr_info("Filling RSB on context switch\n"); > > + } > > Missing an option to turn this off.
Deliberately so. You can already boot with 'spectre_v2=off' to turn off the mitigations. We are not intending to permit all the bullshit micro- management of IBRS=3/IBPB=2/RSB=π nonsense.
If you choose retpoline, you get the RSB stuffing which is appropriate along with that. With IBRS, you get the RSB stuffing which is appropriate with that. You don't get command line or sysfs tunables to mess it. You *do* have the source code, if you really want to make changes. Don't.[unhandled content-type:application/x-pkcs7-signature] | |