Re: [PATCH v2 3/3] x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation

2018-09-03 Thread Thomas Gleixner
On Mon, 3 Sep 2018, Peter Zijlstra wrote: > On Mon, Sep 03, 2018 at 04:34:44PM +0200, Peter Zijlstra wrote: > > On Mon, Sep 03, 2018 at 02:45:31PM +0200, Jiri Kosina wrote: > > > > > +static bool __init stibp_needed(void) > > > +{ > > > + return (cpu_smt_control != CPU_SMT_NOT_SUPPORTED && > > > +

Re: [PATCH v2 3/3] x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation

2018-09-03 Thread Peter Zijlstra
On Mon, Sep 03, 2018 at 04:34:44PM +0200, Peter Zijlstra wrote: > On Mon, Sep 03, 2018 at 02:45:31PM +0200, Jiri Kosina wrote: > > > +static bool __init stibp_needed(void) > > +{ > > + return (cpu_smt_control != CPU_SMT_NOT_SUPPORTED && > > + boot_cpu_has(X86_FEATURE_STIBP)); >

Re: [PATCH v2 3/3] x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation

2018-09-03 Thread Peter Zijlstra
On Mon, Sep 03, 2018 at 02:45:31PM +0200, Jiri Kosina wrote: > +static bool __init stibp_needed(void) > +{ > + return (cpu_smt_control != CPU_SMT_NOT_SUPPORTED && > + boot_cpu_has(X86_FEATURE_STIBP)); > +} Should that not be: ((cpu_smt_control != CPU_SMT_NOT_SUPPO

[PATCH v2 3/3] x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation

2018-09-03 Thread Jiri Kosina
From: Jiri Kosina STIBP is a feature provided by certain Intel ucodes / CPUs. This feature (once enabled) prevents cross-hyperthread control of decisions made by indirect branch predictors. Enable this feature if - the CPU is vulnerable to spectre v2 - the CPU supports SMT - spectre_v2 mitigati