Messages in this thread | | | Date | Mon, 12 Feb 2018 12:50:02 +0100 | From | Peter Zijlstra <> | Subject | Re: [tip:x86/pti] x86/speculation: Use IBRS if available before calling into firmware |
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On Mon, Feb 12, 2018 at 11:22:11AM +0100, Ingo Molnar wrote: > > +static inline void firmware_restrict_branch_speculation_start(void) > > +{ > > + alternative_msr_write(MSR_IA32_SPEC_CTRL, SPEC_CTRL_IBRS, > > + X86_FEATURE_USE_IBRS_FW); > > +} > > + > > +static inline void firmware_restrict_branch_speculation_end(void) > > +{ > > + alternative_msr_write(MSR_IA32_SPEC_CTRL, 0, > > + X86_FEATURE_USE_IBRS_FW); > > BTW., there's a detail that only occurred to me today, this enabling/disabling > sequence is not NMI safe, and it might be called from NMI context:
Wait, we're doing firmware from NMI? That sounds like a _REALLY_ bad idea.
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