4.18-stable review patch. If anyone has any objections, please let me know.
------------------
From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
The kernel unnecessarily prevents late microcode loading when SMT is
disabled. It should be safe to allow it if all the primary threads are
online.
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Acked-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/microcode/core.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -509,12 +509,20 @@ static struct platform_device *microcode
static int check_online_cpus(void)
{
- if (num_online_cpus() == num_present_cpus())
- return 0;
+ unsigned int cpu;
- pr_err("Not all CPUs online, aborting microcode update.\n");
+ /*
+ * Make sure all CPUs are online. It's fine for SMT to be disabled if
+ * all the primary threads are still online.
+ */
+ for_each_present_cpu(cpu) {
+ if (topology_is_primary_thread(cpu) && !cpu_online(cpu)) {
+ pr_err("Not all CPUs online, aborting microcode update.\n");
+ return -EINVAL;
+ }
+ }
- return -EINVAL;
+ return 0;
}
static atomic_t late_cpus_in;
