[MODERATED] [PATCH] Late microcode

* [MODERATED] [PATCH] Late microcode
@ 2018-08-09 19:03 Josh Poimboeuf
  2018-08-09 19:13 ` Thomas Gleixner
  0 siblings, 1 reply; 6+ messages in thread
From: Josh Poimboeuf @ 2018-08-09 19:03 UTC (permalink / raw)
  To: speck

From: Josh Poimboeuf <jpoimboe@redhat.com>
Subject: [PATCH] x86/microcode: Allow late microcode loading with SMT disabled

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@redhat.com>
---
 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 08286269fd24..b9bc8a1a584e 100644
--- 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_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 atomic_t late_cpus_in;
-- 
2.17.1

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