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(&microcode_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(&microcode_mutex);

+

+put:

 	put_online_cpus();

 	if (!ret)

-- 

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