From da540c063b06b18f77168c8a52ee5a9c783a7481 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 10 Aug 2018 08:31:10 +0100 Subject: [PATCH] x86/microcode: Allow late microcode loading with SMT disabled commit 07d981ad4cf1e78361c6db1c28ee5ba105f96cc1 upstream 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 Acked-by: Borislav Petkov Signed-off-by: David Woodhouse Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/cpu/microcode/core.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index 2da1c6a..b53a657 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -386,12 +386,20 @@ static struct platform_device *microcode_pdev; 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 int reload_for_cpu(int cpu) -- 2.7.4