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authorJiri Kosina <jkosina@suse.cz>2018-09-25 14:38:55 +0200
committerThomas Gleixner <tglx@linutronix.de>2018-09-26 14:26:52 +0200
commit53c613fe6349994f023245519265999eed75957f (patch)
treeb4cc05de3a6421aa9dadc5de257371c9cb677674 /lib
parentdbfe2953f63c640463c630746cd5d9de8b2f63ae (diff)
x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation
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 and has SMT siblings online - spectre_v2 mitigation autoselection is enabled (default) After some previous discussion, this leaves STIBP on all the time, as wrmsr on crossing kernel boundary is a no-no. This could perhaps later be a bit more optimized (like disabling it in NOHZ, experiment with disabling it in idle, etc) if needed. Note that the synchronization of the mask manipulation via newly added spec_ctrl_mutex is currently not strictly needed, as the only updater is already being serialized by cpu_add_remove_lock, but let's make this a little bit more future-proof. Signed-off-by: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "WoodhouseDavid" <dwmw@amazon.co.uk> Cc: Andi Kleen <ak@linux.intel.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: "SchauflerCasey" <casey.schaufler@intel.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/nycvar.YFH.7.76.1809251438240.15880@cbobk.fhfr.pm
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