A-Team_Digital_Solutions/android_kernel_motorola_sm6375
Watch
2
0
Fork
You've already forked android_kernel_motorola_sm6375
 0
mirror of https://github.com/BobTheBlinker/android_kernel_motorola_sm6375.git synced 2026-10-28 02:32:09 -04:00
Code Issues Projects Releases Packages Wiki Activity

x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation

Browse source 
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 <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc:  "WoodhouseDavid" <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Tim Chen <[email protected]>
Cc:  "SchauflerCasey" <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
This commit is contained in:
Jiri Kosina 2018-09-25 14:38:55 +02:00 • committed by Thomas Gleixner
commit 53c613fe63
2 changed files with 61 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

11
kernel/cpu.c
View file

@ -2025,6 +2025,12 @@ static void cpuhp_online_cpu_device(unsigned int cpu)
kobject_uevent(&dev->kobj, KOBJ_ONLINE);
}
/*
* Architectures that need SMT-specific errata handling during SMT hotplug
* should override this.
*/
void __weak arch_smt_update(void) { };
static int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
{
int cpu, ret = 0;
@ -2051,8 +2057,10 @@ static int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
*/
cpuhp_offline_cpu_device(cpu);
}
if (!ret)
if (!ret) {
cpu_smt_control = ctrlval;
arch_smt_update();
}
cpu_maps_update_done();
return ret;
}
@ -2063,6 +2071,7 @@ static int cpuhp_smt_enable(void)
cpu_maps_update_begin();
cpu_smt_control = CPU_SMT_ENABLED;
arch_smt_update();
for_each_present_cpu(cpu) {
/* Skip online CPUs and CPUs on offline nodes */
if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))