diff options
| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2018-07-25 10:36:45 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-08-15 18:12:57 +0200 |
| commit | c6613521abbc2685ef334af32e455589d14f1d8d (patch) | |
| tree | 39acdbf4becf626319fe7f7f0dc313ce0192014c /kernel/cpu.c | |
| parent | 40b696da70cfcd1d38be557c3bc7d87cfa25dae6 (diff) | |
| download | linux-stable-c6613521abbc2685ef334af32e455589d14f1d8d.tar.gz linux-stable-c6613521abbc2685ef334af32e455589d14f1d8d.tar.bz2 linux-stable-c6613521abbc2685ef334af32e455589d14f1d8d.zip | |
cpu/hotplug: detect SMT disabled by BIOS
commit 73d5e2b472640b1fcdb61ae8be389912ef211bda upstream
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>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 877437989a28..5787d5e043da 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -2137,6 +2137,15 @@ 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); } |