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| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2018-07-24 18:17:40 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-08-15 17:37:31 +0200 |
| commit | 89f5f7582732de8845e98c23bccae46a6252a601 (patch) | |
| tree | 9e6a19205f7a4f8c199a7b9e5a84270f4d883800 | |
| parent | 00cfc2f506a93719eb6a3dd739108568cf6d441a (diff) | |
| download | linux-89f5f7582732de8845e98c23bccae46a6252a601.tar.gz | |
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -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 38602f962ffe8..7bc26139d99c4 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); } |