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From 30ec26da9967d0d785abc24073129a34c3211777 Mon Sep 17 00:00:00 2001
From: Ashok Raj <ashok.raj@intel.com>
Date: Wed, 28 Feb 2018 11:28:43 +0100
Subject: x86/microcode: Do not upload microcode if CPUs are offline
Avoid loading microcode if any of the CPUs are offline, and issue a
warning. Having different microcode revisions on the system at any time
is outright dangerous.
[ Borislav: Massage changelog. ]
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Tested-by: Ashok Raj <ashok.raj@intel.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Arjan Van De Ven <arjan.van.de.ven@intel.com>
Link: http://lkml.kernel.org/r/1519352533-15992-4-git-send-email-ashok.raj@intel.com
Link: https://lkml.kernel.org/r/20180228102846.13447-5-bp@alien8.de
---
arch/x86/kernel/cpu/microcode/core.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 6337065..fa32cb3 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -486,6 +486,16 @@ static void __exit microcode_dev_exit(void)
/* fake device for request_firmware */
static struct platform_device *microcode_pdev;
+static int check_online_cpus(void)
+{
+ if (num_online_cpus() == num_present_cpus())
+ return 0;
+
+ pr_err("Not all CPUs online, aborting microcode update.\n");
+
+ return -EINVAL;
+}
+
static enum ucode_state reload_for_cpu(int cpu)
{
struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
@@ -519,7 +529,13 @@ static ssize_t reload_store(struct device *dev,
return size;
get_online_cpus();
+
+ ret = check_online_cpus();
+ if (ret)
+ goto put;
+
mutex_lock(µcode_mutex);
+
for_each_online_cpu(cpu) {
tmp_ret = reload_for_cpu(cpu);
if (tmp_ret > UCODE_NFOUND) {
@@ -538,6 +554,8 @@ static ssize_t reload_store(struct device *dev,
microcode_check();
mutex_unlock(µcode_mutex);
+
+put:
put_online_cpus();
if (!ret)
--
cgit v1.1
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