• Jiri Kosina's avatar
    x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation · 8a13906a
    Jiri Kosina authored
    commit 53c613fe upstream.
    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: default avatarJiri Kosina <jkosina@suse.cz>
    Signed-off-by: default avatarThomas 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.pmSigned-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
bugs.c 24.8 KB