[PATCH] Fix microcode-related suspend problem

[Rafael J. Wysocki]

Hi,

This patch appeard on LMKL six days ago and there have not been any negative
comments since then, so I think I can try to make it official.

---
From: Rafael J. Wysocki <rjw@xxxxxxx>

Fix the regression resulting from the recent change of suspend code ordering
that causes systems based on Intel x86 CPUs using the microcode driver to
hang during the resume.

The problem occurs since the microcode driver uses request_firmware() in its
CPU hotplug notifier, which is called after tasks has been frozen and hangs.
It can be fixed by telling the microcode driver to use the microcode stored in
memory during the resume instead of trying to load it from disk.

Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
---
 arch/i386/kernel/microcode.c |   71 ++++++++++++++++++++++++++++++++++++++++---
 include/linux/cpu.h          |    2 +
 kernel/cpu.c                 |   32 +++++++++----------
 3 files changed, 85 insertions(+), 20 deletions(-)

Index: linux-2.6.21-rc5/arch/i386/kernel/microcode.c
===================================================================
--- linux-2.6.21-rc5.orig/arch/i386/kernel/microcode.c
+++ linux-2.6.21-rc5/arch/i386/kernel/microcode.c
@@ -567,6 +567,53 @@ static int cpu_request_microcode(int cpu
 	return error;
 }
 
+static int apply_microcode_on_cpu(int cpu)
+{
+	struct cpuinfo_x86 *c = cpu_data + cpu;
+	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
+	cpumask_t old;
+	unsigned int val[2];
+	int err = 0;
+
+	if (!uci->mc)
+		return -EINVAL;
+
+	old = current->cpus_allowed;
+	set_cpus_allowed(current, cpumask_of_cpu(cpu));
+
+	/* Check if the microcode we have in memory matches the CPU */
+	if (c->x86_vendor != X86_VENDOR_INTEL || c->x86 < 6 ||
+	    cpu_has(c, X86_FEATURE_IA64) || uci->sig != cpuid_eax(0x00000001))
+		err = -EINVAL;
+
+	if (!err && ((c->x86_model >= 5) || (c->x86 > 6))) {
+		/* get processor flags from MSR 0x17 */
+		rdmsr(MSR_IA32_PLATFORM_ID, val[0], val[1]);
+		if (uci->pf != (1 << ((val[1] >> 18) & 7)))
+			err = -EINVAL;
+	}
+
+	if (!err) {
+		wrmsr(MSR_IA32_UCODE_REV, 0, 0);
+		/* see notes above for revision 1.07.  Apparent chip bug */
+		sync_core();
+		/* get the current revision from MSR 0x8B */
+		rdmsr(MSR_IA32_UCODE_REV, val[0], val[1]);
+		if (uci->rev != val[1])
+			err = -EINVAL;
+	}
+
+	if (!err)
+		apply_microcode(cpu);
+	else
+		printk(KERN_ERR "microcode: Could not apply microcode to CPU%d:"
+			" sig=0x%x, pf=0x%x, rev=0x%x\n",
+			cpu, uci->sig, uci->pf, uci->rev);
+
+	set_cpus_allowed(current, old);
+	return err;
+}
+
 static void microcode_init_cpu(int cpu)
 {
 	cpumask_t old;
@@ -577,7 +624,8 @@ static void microcode_init_cpu(int cpu)
 	set_cpus_allowed(current, cpumask_of_cpu(cpu));
 	mutex_lock(&microcode_mutex);
 	collect_cpu_info(cpu);
-	if (uci->valid && system_state == SYSTEM_RUNNING)
+	if (uci->valid && system_state == SYSTEM_RUNNING &&
+	    !suspend_cpu_hotplug)
 		cpu_request_microcode(cpu);
 	mutex_unlock(&microcode_mutex);
 	set_cpus_allowed(current, old);
@@ -663,13 +711,24 @@ static int mc_sysdev_add(struct sys_devi
 		return 0;
 
 	pr_debug("Microcode:CPU %d added\n", cpu);
-	memset(uci, 0, sizeof(*uci));
+	/* If suspend_cpu_hotplug is set, the system is resuming and we should
+	 * use the data from before the suspend.
+	 */
+	if (suspend_cpu_hotplug) {
+		err = apply_microcode_on_cpu(cpu);
+		if (err)
+			microcode_fini_cpu(cpu);
+	}
+	if (!uci->valid)
+		memset(uci, 0, sizeof(*uci));
 
 	err = sysfs_create_group(&sys_dev->kobj, &mc_attr_group);
 	if (err)
 		return err;
 
-	microcode_init_cpu(cpu);
+	if (!uci->valid)
+		microcode_init_cpu(cpu);
+
 	return 0;
 }
 
@@ -680,7 +739,11 @@ static int mc_sysdev_remove(struct sys_d
 	if (!cpu_online(cpu))
 		return 0;
 	pr_debug("Microcode:CPU %d removed\n", cpu);
-	microcode_fini_cpu(cpu);
+	/* If suspend_cpu_hotplug is set, the system is suspending and we should
+	 * keep the microcode in memory for the resume.
+	 */
+	if (!suspend_cpu_hotplug)
+		microcode_fini_cpu(cpu);
 	sysfs_remove_group(&sys_dev->kobj, &mc_attr_group);
 	return 0;
 }
Index: linux-2.6.21-rc5/include/linux/cpu.h
===================================================================
--- linux-2.6.21-rc5.orig/include/linux/cpu.h
+++ linux-2.6.21-rc5/include/linux/cpu.h
@@ -127,6 +127,8 @@ static inline int cpu_is_offline(int cpu
 #endif		/* CONFIG_HOTPLUG_CPU */
 
 #ifdef CONFIG_SUSPEND_SMP
+extern int suspend_cpu_hotplug;
+
 extern int disable_nonboot_cpus(void);
 extern void enable_nonboot_cpus(void);
 #else
Index: linux-2.6.21-rc5/kernel/cpu.c
===================================================================
--- linux-2.6.21-rc5.orig/kernel/cpu.c
+++ linux-2.6.21-rc5/kernel/cpu.c
@@ -254,6 +254,12 @@ int __cpuinit cpu_up(unsigned int cpu)
 }
 
 #ifdef CONFIG_SUSPEND_SMP
+/* Needed to prevent the microcode driver from requesting firmware in its CPU
+ * hotplug notifier during the suspend/resume.
+ */
+int suspend_cpu_hotplug;
+EXPORT_SYMBOL(suspend_cpu_hotplug);
+
 static cpumask_t frozen_cpus;
 
 int disable_nonboot_cpus(void)
@@ -261,16 +267,8 @@ int disable_nonboot_cpus(void)
 	int cpu, first_cpu, error = 0;
 
 	mutex_lock(&cpu_add_remove_lock);
-	first_cpu = first_cpu(cpu_present_map);
-	if (!cpu_online(first_cpu)) {
-		error = _cpu_up(first_cpu);
-		if (error) {
-			printk(KERN_ERR "Could not bring CPU%d up.\n",
-				first_cpu);
-			goto out;
-		}
-	}
-
+	suspend_cpu_hotplug = 1;
+	first_cpu = first_cpu(cpu_online_map);
 	/* We take down all of the non-boot CPUs in one shot to avoid races
 	 * with the userspace trying to use the CPU hotplug at the same time
 	 */
@@ -296,7 +294,7 @@ int disable_nonboot_cpus(void)
 	} else {
 		printk(KERN_ERR "Non-boot CPUs are not disabled\n");
 	}
-out:
+	suspend_cpu_hotplug = 0;
 	mutex_unlock(&cpu_add_remove_lock);
 	return error;
 }
@@ -308,20 +306,22 @@ void enable_nonboot_cpus(void)
 	/* Allow everyone to use the CPU hotplug again */
 	mutex_lock(&cpu_add_remove_lock);
 	cpu_hotplug_disabled = 0;
-	mutex_unlock(&cpu_add_remove_lock);
 	if (cpus_empty(frozen_cpus))
-		return;
+		goto out;
 
+	suspend_cpu_hotplug = 1;
 	printk("Enabling non-boot CPUs ...\n");
 	for_each_cpu_mask(cpu, frozen_cpus) {
-		error = cpu_up(cpu);
+		error = _cpu_up(cpu);
 		if (!error) {
 			printk("CPU%d is up\n", cpu);
 			continue;
 		}
-		printk(KERN_WARNING "Error taking CPU%d up: %d\n",
-			cpu, error);
+		printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
 	}
 	cpus_clear(frozen_cpus);
+	suspend_cpu_hotplug = 0;
+out:
+	mutex_unlock(&cpu_add_remove_lock);
 }
 #endif
-
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