diff options
author | Jiri Kosina <jkosina@suse.cz> | 2018-09-25 14:38:55 +0200 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-05-16 19:45:10 +0200 |
commit | dc23d0241b97bd6bb8fc1dfce27c758ef58ccd54 (patch) | |
tree | 19b1fc3bd2220b81592a4794117fd43758eaf1c1 /arch/avr32 | |
parent | 4a215a1155ce2be31832ed1f5075cb57bb2818ec (diff) |
x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation
commit 53c613fe6349994f023245519265999eed75957f 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: 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>
Link: https://lkml.kernel.org/r/nycvar.YFH.7.76.1809251438240.15880@cbobk.fhfr.pm
[bwh: Backported to 4.4:
- Don't add any calls to arch_smt_update() yet. They will be introduced by
"x86/speculation: Rework SMT state change".
- Use IS_ENABLED(CONFIG_SMP) instead of cpu_smt_control for now. This
will be fixed by "x86/speculation: Rework SMT state change".]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/avr32')
0 files changed, 0 insertions, 0 deletions