diff options
| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2018-07-24 18:17:40 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2018-07-24 18:17:40 +0200 |
| commit | 73d5e2b472640b1fcdb61ae8be389912ef211bda (patch) | |
| tree | a0b859dfb525e4a89dc068194177108d5745f46d /kernel/cpu.c | |
| parent | 1949f9f49792d65dba2090edddbe36a5f02e3ba3 (diff) | |
cpu/hotplug: detect SMT disabled by BIOS
If SMT is disabled in BIOS, the CPU code doesn't properly detect it.
The /sys/devices/system/cpu/smt/control file shows 'on', and the 'l1tf'
vulnerabilities file shows SMT as vulnerable.
Fix it by forcing 'cpu_smt_control' to CPU_SMT_NOT_SUPPORTED in such a
case. Unfortunately the detection can only be done after bringing all
the CPUs online, so we have to overwrite any previous writes to the
variable.
Reported-by: Joe Mario <jmario@redhat.com>
Tested-by: Jiri Kosina <jkosina@suse.cz>
Fixes: f048c399e0f7 ("x86/topology: Provide topology_smt_supported()")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Diffstat (limited to 'kernel/cpu.c')
| -rw-r--r-- | kernel/cpu.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c index 37eec872042b..2bc3d2f5b2a5 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -2125,6 +2125,15 @@ static const struct attribute_group cpuhp_smt_attr_group = { static int __init cpu_smt_state_init(void) { + /* + * If SMT was disabled by BIOS, detect it here, after the CPUs have + * been brought online. This ensures the smt/l1tf sysfs entries are + * consistent with reality. Note this may overwrite cpu_smt_control's + * previous setting. + */ + if (topology_max_smt_threads() == 1) + cpu_smt_control = CPU_SMT_NOT_SUPPORTED; + return sysfs_create_group(&cpu_subsys.dev_root->kobj, &cpuhp_smt_attr_group); } |