x86: microcode: use smp_call_function_single instead of set_cpus_allowed, cleanup of synchronization logic

* Solve issues described in 6f66cbc63081fd70e3191b4dbb796746780e5ae1
  in a way that doesn't resort to set_cpus_allowed();

* in fact, only collect_cpu_info and apply_microcode callbacks
  must run on a target cpu, others will do just fine on any other.
  smp_call_function_single() (as suggested by Ingo) is used to run
  these callbacks on a target cpu.

* cleanup of synchronization logic of the 'microcode_core' part

  The generic 'microcode_core' part guarantees that only a single cpu
  (be it a full-fledged cpu, one of the cores or HT)
  is being updated at any particular moment of time.

  In general, there is no need for any additional sync. mechanism in
  arch-specific parts (the patch removes existing spinlocks).

  See also the "Synchronization" section in microcode_core.c.

* return -EINVAL instead of -1 (which is translated into -EPERM) in
  microcode_write(), reload_cpu() and mc_sysdev_add(). Other suggestions
  for an error code?

* use 'enum ucode_state' as return value of request_microcode_{fw, user}
  to gain more flexibility by distinguishing between real error cases
  and situations when an appropriate ucode was not found (which is not an
  error per-se).

* some minor cleanups

Thanks a lot to Hugh Dickins for review/suggestions/testing!

   Reference: http://marc.info/?l=linux-kernel&m=124025889012541&w=2

[ Impact: refactor and clean up microcode driver locking code ]

Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Acked-by: Hugh Dickins <hugh@veritas.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andreas Herrmann <andreas.herrmann3@amd.com>
Cc: Peter Oruba <peter.oruba@amd.com>
Cc: Arjan van de Ven <arjan@infradead.org>
LKML-Reference: <1242078507.5560.9.camel@earth>
[ did some more cleanups ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
 arch/x86/include/asm/microcode.h  |   25 ++
 arch/x86/kernel/microcode_amd.c   |   58 ++----
 arch/x86/kernel/microcode_core.c  |  326 +++++++++++++++++++++-----------------
 arch/x86/kernel/microcode_intel.c |   92 +++-------
 4 files changed, 261 insertions(+), 240 deletions(-)

(~20 new comment lines)

4 files changed, 262 insertions, 240 deletions

diff --git a/arch/x86/include/asm/microcode.h b/arch/x86/include/asm/microcode.h
index c882664716c1..ef51b501e22a 100644
--- a/arch/x86/include/asm/microcode.h
+++ b/arch/x86/include/asm/microcode.h
@@ -9,20 +9,31 @@ struct cpu_signature {
 
 struct device;
 
+enum ucode_state { UCODE_ERROR, UCODE_OK, UCODE_NFOUND };
+
 struct microcode_ops {
-        int  (*request_microcode_user) (int cpu, const void __user *buf, size_t size);
-        int  (*request_microcode_fw) (int cpu, struct device *device);
+        enum ucode_state (*request_microcode_user) (int cpu,
+                                const void __user *buf, size_t size);
 
-        void (*apply_microcode) (int cpu);
+        enum ucode_state (*request_microcode_fw) (int cpu,
+                                struct device *device);
 
-        int  (*collect_cpu_info) (int cpu, struct cpu_signature *csig);
         void (*microcode_fini_cpu) (int cpu);
+
+        /*
+         * The generic 'microcode_core' part guarantees that
+         * the callbacks below run on a target cpu when they
+         * are being called.
+         * See also the "Synchronization" section in microcode_core.c.
+         */
+        int (*apply_microcode) (int cpu);
+        int (*collect_cpu_info) (int cpu, struct cpu_signature *csig);
 };
 
 struct ucode_cpu_info {
-        struct cpu_signature cpu_sig;
-        int valid;
-        void *mc;
+        struct cpu_signature    cpu_sig;
+        int                     valid;
+        void                    *mc;
 };
 extern struct ucode_cpu_info ucode_cpu_info[];
 
diff --git a/arch/x86/kernel/microcode_amd.c b/arch/x86/kernel/microcode_amd.c
index 453b5795a5c6..c8be20f16447 100644
--- a/arch/x86/kernel/microcode_amd.c
+++ b/arch/x86/kernel/microcode_amd.c
@@ -13,25 +13,13 @@
  *  Licensed under the terms of the GNU General Public
  *  License version 2. See file COPYING for details.
  */
-#include <linux/platform_device.h>
-#include <linux/capability.h>
-#include <linux/miscdevice.h>
 #include <linux/firmware.h>
-#include <linux/spinlock.h>
-#include <linux/cpumask.h>
 #include <linux/pci_ids.h>
 #include <linux/uaccess.h>
 #include <linux/vmalloc.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
-#include <linux/mutex.h>
-#include <linux/sched.h>
-#include <linux/init.h>
-#include <linux/slab.h>
-#include <linux/cpu.h>
 #include <linux/pci.h>
-#include <linux/fs.h>
-#include <linux/mm.h>
 
 #include <asm/microcode.h>
 #include <asm/processor.h>
@@ -79,9 +67,6 @@ struct microcode_amd {
 #define UCODE_CONTAINER_SECTION_HDR     8
 #define UCODE_CONTAINER_HEADER_SIZE     12
 
-/* serialize access to the physical write */
-static DEFINE_SPINLOCK(microcode_update_lock);
-
 static struct equiv_cpu_entry *equiv_cpu_table;
 
 static int collect_cpu_info_amd(int cpu, struct cpu_signature *csig)
@@ -144,9 +129,8 @@ static int get_matching_microcode(int cpu, void *mc, int rev)
         return 1;
 }
 
-static void apply_microcode_amd(int cpu)
+static int apply_microcode_amd(int cpu)
 {
-        unsigned long flags;
         u32 rev, dummy;
         int cpu_num = raw_smp_processor_id();
         struct ucode_cpu_info *uci = ucode_cpu_info + cpu_num;
@@ -156,25 +140,25 @@ static void apply_microcode_amd(int cpu)
         BUG_ON(cpu_num != cpu);
 
         if (mc_amd == NULL)
-                return;
+                return 0;
 
-        spin_lock_irqsave(&microcode_update_lock, flags);
         wrmsrl(MSR_AMD64_PATCH_LOADER, (u64)(long)&mc_amd->hdr.data_code);
         /* get patch id after patching */
         rdmsr(MSR_AMD64_PATCH_LEVEL, rev, dummy);
-        spin_unlock_irqrestore(&microcode_update_lock, flags);
 
         /* check current patch id and patch's id for match */
         if (rev != mc_amd->hdr.patch_id) {
                 printk(KERN_ERR "microcode: CPU%d: update failed "
                        "(for patch_level=0x%x)\n", cpu, mc_amd->hdr.patch_id);
-                return;
+                return -1;
         }
 
         printk(KERN_INFO "microcode: CPU%d: updated (new patch_level=0x%x)\n",
                cpu, rev);
 
         uci->cpu_sig.rev = rev;
+
+        return 0;
 }
 
 static int get_ucode_data(void *to, const u8 *from, size_t n)
@@ -263,7 +247,8 @@ static void free_equiv_cpu_table(void)
         }
 }
 
-static int generic_load_microcode(int cpu, const u8 *data, size_t size)
+static enum ucode_state
+generic_load_microcode(int cpu, const u8 *data, size_t size)
 {
         struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
         const u8 *ucode_ptr = data;
@@ -272,12 +257,13 @@ static int generic_load_microcode(int cpu, const u8 *data, size_t size)
         int new_rev = uci->cpu_sig.rev;
         unsigned int leftover;
         unsigned long offset;
+        enum ucode_state state = UCODE_OK;
 
         offset = install_equiv_cpu_table(ucode_ptr);
         if (!offset) {
                 printk(KERN_ERR "microcode: failed to create "
                        "equivalent cpu table\n");
-                return -EINVAL;
+                return UCODE_ERROR;
         }
 
         ucode_ptr += offset;
@@ -312,28 +298,27 @@ static int generic_load_microcode(int cpu, const u8 *data, size_t size)
                         pr_debug("microcode: CPU%d found a matching microcode "
                                  "update with version 0x%x (current=0x%x)\n",
                                  cpu, new_rev, uci->cpu_sig.rev);
-                } else
+                } else {
                         vfree(new_mc);
-        }
+                        state = UCODE_ERROR;
+                }
+        } else
+                state = UCODE_NFOUND;
 
         free_equiv_cpu_table();
 
-        return (int)leftover;
+        return state;
 }
 
-static int request_microcode_fw(int cpu, struct device *device)
+static enum ucode_state request_microcode_fw(int cpu, struct device *device)
 {
         const char *fw_name = "amd-ucode/microcode_amd.bin";
         const struct firmware *firmware;
-        int ret;
-
-        /* We should bind the task to the CPU */
-        BUG_ON(cpu != raw_smp_processor_id());
+        enum ucode_state ret;
 
-        ret = request_firmware(&firmware, fw_name, device);
-        if (ret) {
+        if (request_firmware(&firmware, fw_name, device)) {
                 printk(KERN_ERR "microcode: failed to load file %s\n", fw_name);
-                return ret;
+                return UCODE_NFOUND;
         }
 
         ret = generic_load_microcode(cpu, firmware->data, firmware->size);
@@ -343,11 +328,12 @@ static int request_microcode_fw(int cpu, struct device *device)
         return ret;
 }
 
-static int request_microcode_user(int cpu, const void __user *buf, size_t size)
+static enum ucode_state
+request_microcode_user(int cpu, const void __user *buf, size_t size)
 {
         printk(KERN_INFO "microcode: AMD microcode update via "
                "/dev/cpu/microcode not supported\n");
-        return -1;
+        return UCODE_ERROR;
 }
 
 static void microcode_fini_cpu_amd(int cpu)
diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
index 98c470c069d1..9c4461501fcb 100644
--- a/arch/x86/kernel/microcode_core.c
+++ b/arch/x86/kernel/microcode_core.c
@@ -71,27 +71,18 @@
  *              Thanks to Stuart Swales for pointing out this bug.
  */
 #include <linux/platform_device.h>
-#include <linux/capability.h>
 #include <linux/miscdevice.h>
-#include <linux/firmware.h>
+#include <linux/capability.h>
 #include <linux/smp_lock.h>
-#include <linux/spinlock.h>
-#include <linux/cpumask.h>
-#include <linux/uaccess.h>
-#include <linux/vmalloc.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
-#include <linux/sched.h>
-#include <linux/init.h>
-#include <linux/slab.h>
 #include <linux/cpu.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
 
 #include <asm/microcode.h>
 #include <asm/processor.h>
-#include <asm/msr.h>
 
 MODULE_DESCRIPTION("Microcode Update Driver");
 MODULE_AUTHOR("Tigran Aivazian <tigran@aivazian.fsnet.co.uk>");
@@ -101,36 +92,110 @@ MODULE_LICENSE("GPL");
 
 static struct microcode_ops     *microcode_ops;
 
-/* no concurrent ->write()s are allowed on /dev/cpu/microcode */
+/*
+ * Synchronization.
+ *
+ * All non cpu-hotplug-callback call sites use:
+ *
+ * - microcode_mutex to synchronize with each other;
+ * - get/put_online_cpus() to synchronize with
+ *   the cpu-hotplug-callback call sites.
+ *
+ * We guarantee that only a single cpu is being
+ * updated at any particular moment of time.
+ */
 static DEFINE_MUTEX(microcode_mutex);
 
 struct ucode_cpu_info           ucode_cpu_info[NR_CPUS];
 EXPORT_SYMBOL_GPL(ucode_cpu_info);
 
+/*
+ * Operations that are run on a target cpu:
+ */
+
+struct cpu_info_ctx {
+        struct cpu_signature    *cpu_sig;
+        int                     err;
+};
+
+static void collect_cpu_info_local(void *arg)
+{
+        struct cpu_info_ctx *ctx = arg;
+
+        ctx->err = microcode_ops->collect_cpu_info(smp_processor_id(),
+                                                   ctx->cpu_sig);
+}
+
+static int collect_cpu_info_on_target(int cpu, struct cpu_signature *cpu_sig)
+{
+        struct cpu_info_ctx ctx = { .cpu_sig = cpu_sig, .err = 0 };
+        int ret;
+
+        ret = smp_call_function_single(cpu, collect_cpu_info_local, &ctx, 1);
+        if (!ret)
+                ret = ctx.err;
+
+        return ret;
+}
+
+static int collect_cpu_info(int cpu)
+{
+        struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
+        int ret;
+
+        memset(uci, 0, sizeof(*uci));
+
+        ret = collect_cpu_info_on_target(cpu, &uci->cpu_sig);
+        if (!ret)
+                uci->valid = 1;
+
+        return ret;
+}
+
+struct apply_microcode_ctx {
+        int err;
+};
+
+static void apply_microcode_local(void *arg)
+{
+        struct apply_microcode_ctx *ctx = arg;
+
+        ctx->err = microcode_ops->apply_microcode(smp_processor_id());
+}
+
+static int apply_microcode_on_target(int cpu)
+{
+        struct apply_microcode_ctx ctx = { .err = 0 };
+        int ret;
+
+        ret = smp_call_function_single(cpu, apply_microcode_local, &ctx, 1);
+        if (!ret)
+                ret = ctx.err;
+
+        return ret;
+}
+
 #ifdef CONFIG_MICROCODE_OLD_INTERFACE
 static int do_microcode_update(const void __user *buf, size_t size)
 {
-        cpumask_t old;
         int error = 0;
         int cpu;
 
-        old = current->cpus_allowed;
-
         for_each_online_cpu(cpu) {
                 struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
+                enum ucode_state ustate;
 
                 if (!uci->valid)
                         continue;
 
-                set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
-                error = microcode_ops->request_microcode_user(cpu, buf, size);
-                if (error < 0)
-                        goto out;
-                if (!error)
-                        microcode_ops->apply_microcode(cpu);
+                ustate = microcode_ops->request_microcode_user(cpu, buf, size);
+                if (ustate == UCODE_ERROR) {
+                        error = -1;
+                        break;
+                } else if (ustate == UCODE_OK)
+                        apply_microcode_on_target(cpu);
         }
-out:
-        set_cpus_allowed_ptr(current, &old);
+
         return error;
 }
 
@@ -143,19 +208,17 @@ static int microcode_open(struct inode *unused1, struct file *unused2)
 static ssize_t microcode_write(struct file *file, const char __user *buf,
                                size_t len, loff_t *ppos)
 {
-        ssize_t ret;
+        ssize_t ret = -EINVAL;
 
         if ((len >> PAGE_SHIFT) > num_physpages) {
-                printk(KERN_ERR "microcode: too much data (max %ld pages)\n",
-                       num_physpages);
-                return -EINVAL;
+                pr_err("microcode: too much data (max %ld pages)\n", num_physpages);
+                return ret;
         }
 
         get_online_cpus();
         mutex_lock(&microcode_mutex);
 
-        ret = do_microcode_update(buf, len);
-        if (!ret)
+        if (do_microcode_update(buf, len) == 0)
                 ret = (ssize_t)len;
 
         mutex_unlock(&microcode_mutex);
@@ -165,15 +228,15 @@ static ssize_t microcode_write(struct file *file, const char __user *buf,
 }
 
 static const struct file_operations microcode_fops = {
-        .owner          = THIS_MODULE,
-        .write          = microcode_write,
-        .open           = microcode_open,
+        .owner                  = THIS_MODULE,
+        .write                  = microcode_write,
+        .open                   = microcode_open,
 };
 
 static struct miscdevice microcode_dev = {
-        .minor          = MICROCODE_MINOR,
-        .name           = "microcode",
-        .fops           = &microcode_fops,
+        .minor                  = MICROCODE_MINOR,
+        .name                   = "microcode",
+        .fops                   = &microcode_fops,
 };
 
 static int __init microcode_dev_init(void)
@@ -182,9 +245,7 @@ static int __init microcode_dev_init(void)
 
         error = misc_register(&microcode_dev);
         if (error) {
-                printk(KERN_ERR
-                        "microcode: can't misc_register on minor=%d\n",
-                        MICROCODE_MINOR);
+                pr_err("microcode: can't misc_register on minor=%d\n", MICROCODE_MINOR);
                 return error;
         }
 
@@ -205,42 +266,51 @@ MODULE_ALIAS_MISCDEV(MICROCODE_MINOR);
 /* fake device for request_firmware */
 static struct platform_device   *microcode_pdev;
 
-static long reload_for_cpu(void *unused)
+static int reload_for_cpu(int cpu)
 {
-        struct ucode_cpu_info *uci = ucode_cpu_info + smp_processor_id();
+        struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
         int err = 0;
 
         mutex_lock(&microcode_mutex);
         if (uci->valid) {
-                err = microcode_ops->request_microcode_fw(smp_processor_id(),
-                                                          &microcode_pdev->dev);
-                if (!err)
-                        microcode_ops->apply_microcode(smp_processor_id());
+                enum ucode_state ustate;
+
+                ustate = microcode_ops->request_microcode_fw(cpu, &microcode_pdev->dev);
+                if (ustate == UCODE_OK)
+                        apply_microcode_on_target(cpu);
+                else
+                        if (ustate == UCODE_ERROR)
+                                err = -EINVAL;
         }
         mutex_unlock(&microcode_mutex);
+
         return err;
 }
 
 static ssize_t reload_store(struct sys_device *dev,
                             struct sysdev_attribute *attr,
-                            const char *buf, size_t sz)
+                            const char *buf, size_t size)
 {
-        char *end;
-        unsigned long val = simple_strtoul(buf, &end, 0);
-        int err = 0;
+        unsigned long val;
         int cpu = dev->id;
+        int ret = 0;
+        char *end;
 
+        val = simple_strtoul(buf, &end, 0);
         if (end == buf)
                 return -EINVAL;
+
         if (val == 1) {
                 get_online_cpus();
                 if (cpu_online(cpu))
-                        err = work_on_cpu(cpu, reload_for_cpu, NULL);
+                        ret = reload_for_cpu(cpu);
                 put_online_cpus();
         }
-        if (err)
-                return err;
-        return sz;
+
+        if (!ret)
+                ret = size;
+
+        return ret;
 }
 
 static ssize_t version_show(struct sys_device *dev,
@@ -271,11 +341,11 @@ static struct attribute *mc_default_attrs[] = {
 };
 
 static struct attribute_group mc_attr_group = {
-        .attrs          = mc_default_attrs,
-        .name           = "microcode",
+        .attrs                  = mc_default_attrs,
+        .name                   = "microcode",
 };
 
-static void __microcode_fini_cpu(int cpu)
+static void microcode_fini_cpu(int cpu)
 {
         struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 
@@ -283,103 +353,68 @@ static void __microcode_fini_cpu(int cpu)
         uci->valid = 0;
 }
 
-static void microcode_fini_cpu(int cpu)
-{
-        mutex_lock(&microcode_mutex);
-        __microcode_fini_cpu(cpu);
-        mutex_unlock(&microcode_mutex);
-}
-
-static void collect_cpu_info(int cpu)
+static enum ucode_state microcode_resume_cpu(int cpu)
 {
         struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 
-        memset(uci, 0, sizeof(*uci));
-        if (!microcode_ops->collect_cpu_info(cpu, &uci->cpu_sig))
-                uci->valid = 1;
+        if (!uci->mc)
+                return UCODE_NFOUND;
+
+        pr_debug("microcode: CPU%d updated upon resume\n", cpu);
+        apply_microcode_on_target(cpu);
+
+        return UCODE_OK;
 }
 
-static int microcode_resume_cpu(int cpu)
+static enum ucode_state microcode_init_cpu(int cpu)
 {
-        struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
-        struct cpu_signature nsig;
+        enum ucode_state ustate;
 
-        pr_debug("microcode: CPU%d resumed\n", cpu);
+        if (collect_cpu_info(cpu))
+                return UCODE_ERROR;
 
-        if (!uci->mc)
-                return 1;
+        /* --dimm. Trigger a delayed update? */
+        if (system_state != SYSTEM_RUNNING)
+                return UCODE_NFOUND;
 
-        /*
-         * Let's verify that the 'cached' ucode does belong
-         * to this cpu (a bit of paranoia):
-         */
-        if (microcode_ops->collect_cpu_info(cpu, &nsig)) {
-                __microcode_fini_cpu(cpu);
-                printk(KERN_ERR "failed to collect_cpu_info for resuming cpu #%d\n",
-                                cpu);
-                return -1;
-        }
+        ustate = microcode_ops->request_microcode_fw(cpu, &microcode_pdev->dev);
 
-        if ((nsig.sig != uci->cpu_sig.sig) || (nsig.pf != uci->cpu_sig.pf)) {
-                __microcode_fini_cpu(cpu);
-                printk(KERN_ERR "cached ucode doesn't match the resuming cpu #%d\n",
-                                cpu);
-                /* Should we look for a new ucode here? */
-                return 1;
+        if (ustate == UCODE_OK) {
+                pr_debug("microcode: CPU%d updated upon init\n", cpu);
+                apply_microcode_on_target(cpu);
         }
 
-        return 0;
+        return ustate;
 }
 
-static long microcode_update_cpu(void *unused)
+static enum ucode_state microcode_update_cpu(int cpu)
 {
-        struct ucode_cpu_info *uci = ucode_cpu_info + smp_processor_id();
-        int err = 0;
+        struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
+        enum ucode_state ustate;
 
-        /*
-         * Check if the system resume is in progress (uci->valid != NULL),
-         * otherwise just request a firmware:
-         */
-        if (uci->valid) {
-                err = microcode_resume_cpu(smp_processor_id());
-        } else {
-                collect_cpu_info(smp_processor_id());
-                if (uci->valid && system_state == SYSTEM_RUNNING)
-                        err = microcode_ops->request_microcode_fw(
-                                        smp_processor_id(),
-                                        &microcode_pdev->dev);
-        }
-        if (!err)
-                microcode_ops->apply_microcode(smp_processor_id());
-        return err;
-}
+        if (uci->valid)
+                ustate = microcode_resume_cpu(cpu);
+        else
+                ustate = microcode_init_cpu(cpu);
 
-static int microcode_init_cpu(int cpu)
-{
-        int err;
-        mutex_lock(&microcode_mutex);
-        err = work_on_cpu(cpu, microcode_update_cpu, NULL);
-        mutex_unlock(&microcode_mutex);
-
-        return err;
+        return ustate;
 }
 
 static int mc_sysdev_add(struct sys_device *sys_dev)
 {
         int err, cpu = sys_dev->id;
-        struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 
         if (!cpu_online(cpu))
                 return 0;
 
         pr_debug("microcode: CPU%d added\n", cpu);
-        memset(uci, 0, sizeof(*uci));
 
         err = sysfs_create_group(&sys_dev->kobj, &mc_attr_group);
         if (err)
                 return err;
 
-        err = microcode_init_cpu(cpu);
+        if (microcode_init_cpu(cpu) == UCODE_ERROR)
+                err = -EINVAL;
 
         return err;
 }
@@ -400,19 +435,30 @@ static int mc_sysdev_remove(struct sys_device *sys_dev)
 static int mc_sysdev_resume(struct sys_device *dev)
 {
         int cpu = dev->id;
+        struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 
         if (!cpu_online(cpu))
                 return 0;
 
-        /* only CPU 0 will apply ucode here */
-        microcode_update_cpu(NULL);
+        /*
+         * All non-bootup cpus are still disabled,
+         * so only CPU 0 will apply ucode here.
+         *
+         * Moreover, there can be no concurrent
+         * updates from any other places at this point.
+         */
+        WARN_ON(cpu != 0);
+
+        if (uci->valid && uci->mc)
+                microcode_ops->apply_microcode(cpu);
+
         return 0;
 }
 
 static struct sysdev_driver mc_sysdev_driver = {
-        .add            = mc_sysdev_add,
-        .remove         = mc_sysdev_remove,
-        .resume         = mc_sysdev_resume,
+        .add                    = mc_sysdev_add,
+        .remove                 = mc_sysdev_remove,
+        .resume                 = mc_sysdev_resume,
 };
 
 static __cpuinit int
@@ -425,15 +471,12 @@ mc_cpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu)
         switch (action) {
         case CPU_ONLINE:
         case CPU_ONLINE_FROZEN:
-                if (microcode_init_cpu(cpu))
-                        printk(KERN_ERR "microcode: failed to init CPU%d\n",
-                               cpu);
+                microcode_update_cpu(cpu);
         case CPU_DOWN_FAILED:
         case CPU_DOWN_FAILED_FROZEN:
                 pr_debug("microcode: CPU%d added\n", cpu);
                 if (sysfs_create_group(&sys_dev->kobj, &mc_attr_group))
-                        printk(KERN_ERR "microcode: Failed to create the sysfs "
-                                "group for CPU%d\n", cpu);
+                        pr_err("microcode: Failed to create group for CPU%d\n", cpu);
                 break;
         case CPU_DOWN_PREPARE:
         case CPU_DOWN_PREPARE_FROZEN:
@@ -465,13 +508,10 @@ static int __init microcode_init(void)
                 microcode_ops = init_amd_microcode();
 
         if (!microcode_ops) {
-                printk(KERN_ERR "microcode: no support for this CPU vendor\n");
+                pr_err("microcode: no support for this CPU vendor\n");
                 return -ENODEV;
         }
 
-        error = microcode_dev_init();
-        if (error)
-                return error;
         microcode_pdev = platform_device_register_simple("microcode", -1,
                                                          NULL, 0);
         if (IS_ERR(microcode_pdev)) {
@@ -480,23 +520,31 @@ static int __init microcode_init(void)
         }
 
         get_online_cpus();
+        mutex_lock(&microcode_mutex);
+
         error = sysdev_driver_register(&cpu_sysdev_class, &mc_sysdev_driver);
+
+        mutex_unlock(&microcode_mutex);
         put_online_cpus();
+
         if (error) {
-                microcode_dev_exit();
                 platform_device_unregister(microcode_pdev);
                 return error;
         }
 
+        error = microcode_dev_init();
+        if (error)
+                return error;
+
         register_hotcpu_notifier(&mc_cpu_notifier);
 
-        printk(KERN_INFO
-               "Microcode Update Driver: v" MICROCODE_VERSION
+        pr_info("Microcode Update Driver: v" MICROCODE_VERSION
                " <tigran@aivazian.fsnet.co.uk>,"
                " Peter Oruba\n");
 
         return 0;
 }
+module_init(microcode_init);
 
 static void __exit microcode_exit(void)
 {
@@ -505,16 +553,17 @@ static void __exit microcode_exit(void)
         unregister_hotcpu_notifier(&mc_cpu_notifier);
 
         get_online_cpus();
+        mutex_lock(&microcode_mutex);
+
         sysdev_driver_unregister(&cpu_sysdev_class, &mc_sysdev_driver);
+
+        mutex_unlock(&microcode_mutex);
         put_online_cpus();
 
         platform_device_unregister(microcode_pdev);
 
         microcode_ops = NULL;
 
-        printk(KERN_INFO
-               "Microcode Update Driver: v" MICROCODE_VERSION " removed.\n");
+        pr_info("Microcode Update Driver: v" MICROCODE_VERSION " removed.\n");
 }
-
-module_init(microcode_init);
 module_exit(microcode_exit);
diff --git a/arch/x86/kernel/microcode_intel.c b/arch/x86/kernel/microcode_intel.c
index 149b9ec7c1ab..0d334ddd0a96 100644
--- a/arch/x86/kernel/microcode_intel.c
+++ b/arch/x86/kernel/microcode_intel.c
@@ -70,24 +70,11 @@
  *              Fix sigmatch() macro to handle old CPUs with pf == 0.
  *              Thanks to Stuart Swales for pointing out this bug.
  */
-#include <linux/platform_device.h>
-#include <linux/capability.h>
-#include <linux/miscdevice.h>
 #include <linux/firmware.h>
-#include <linux/smp_lock.h>
-#include <linux/spinlock.h>
-#include <linux/cpumask.h>
 #include <linux/uaccess.h>
-#include <linux/vmalloc.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
-#include <linux/mutex.h>
-#include <linux/sched.h>
-#include <linux/init.h>
-#include <linux/slab.h>
-#include <linux/cpu.h>
-#include <linux/fs.h>
-#include <linux/mm.h>
+#include <linux/vmalloc.h>
 
 #include <asm/microcode.h>
 #include <asm/processor.h>
@@ -150,13 +137,9 @@ struct extended_sigtable {
 
 #define exttable_size(et) ((et)->count * EXT_SIGNATURE_SIZE + EXT_HEADER_SIZE)
 
-/* serialize access to the physical write to MSR 0x79 */
-static DEFINE_SPINLOCK(microcode_update_lock);
-
 static int collect_cpu_info(int cpu_num, struct cpu_signature *csig)
 {
         struct cpuinfo_x86 *c = &cpu_data(cpu_num);
-        unsigned long flags;
         unsigned int val[2];
 
         memset(csig, 0, sizeof(*csig));
@@ -176,18 +159,14 @@ static int collect_cpu_info(int cpu_num, struct cpu_signature *csig)
                 csig->pf = 1 << ((val[1] >> 18) & 7);
         }
 
-        /* serialize access to the physical write to MSR 0x79 */
-        spin_lock_irqsave(&microcode_update_lock, flags);
-
         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], csig->rev);
-        spin_unlock_irqrestore(&microcode_update_lock, flags);
 
-        pr_debug("microcode: collect_cpu_info : sig=0x%x, pf=0x%x, rev=0x%x\n",
-                        csig->sig, csig->pf, csig->rev);
+        printk(KERN_INFO "microcode: CPU%d sig=0x%x, pf=0x%x, revision=0x%x\n",
+                        cpu_num, csig->sig, csig->pf, csig->rev);
 
         return 0;
 }
@@ -318,11 +297,10 @@ get_matching_microcode(struct cpu_signature *cpu_sig, void *mc, int rev)
         return 0;
 }
 
-static void apply_microcode(int cpu)
+static int apply_microcode(int cpu)
 {
         struct microcode_intel *mc_intel;
         struct ucode_cpu_info *uci;
-        unsigned long flags;
         unsigned int val[2];
         int cpu_num;
 
@@ -334,10 +312,7 @@ static void apply_microcode(int cpu)
         BUG_ON(cpu_num != cpu);
 
         if (mc_intel == NULL)
-                return;
-
-        /* serialize access to the physical write to MSR 0x79 */
-        spin_lock_irqsave(&microcode_update_lock, flags);
+                return 0;
 
         /* write microcode via MSR 0x79 */
         wrmsr(MSR_IA32_UCODE_WRITE,
@@ -351,30 +326,32 @@ static void apply_microcode(int cpu)
         /* get the current revision from MSR 0x8B */
         rdmsr(MSR_IA32_UCODE_REV, val[0], val[1]);
 
-        spin_unlock_irqrestore(&microcode_update_lock, flags);
         if (val[1] != mc_intel->hdr.rev) {
-                printk(KERN_ERR "microcode: CPU%d update from revision "
-                                "0x%x to 0x%x failed\n",
-                        cpu_num, uci->cpu_sig.rev, val[1]);
-                return;
+                printk(KERN_ERR "microcode: CPU%d update "
+                                "to revision 0x%x failed\n",
+                        cpu_num, mc_intel->hdr.rev);
+                return -1;
         }
-        printk(KERN_INFO "microcode: CPU%d updated from revision "
-                         "0x%x to 0x%x, date = %04x-%02x-%02x \n",
-                cpu_num, uci->cpu_sig.rev, val[1],
+        printk(KERN_INFO "microcode: CPU%d updated to revision "
+                         "0x%x, date = %04x-%02x-%02x \n",
+                cpu_num, val[1],
                 mc_intel->hdr.date & 0xffff,
                 mc_intel->hdr.date >> 24,
                 (mc_intel->hdr.date >> 16) & 0xff);
 
         uci->cpu_sig.rev = val[1];
+
+        return 0;
 }
 
-static int generic_load_microcode(int cpu, void *data, size_t size,
-                int (*get_ucode_data)(void *, const void *, size_t))
+static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
+                                int (*get_ucode_data)(void *, const void *, size_t))
 {
         struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
         u8 *ucode_ptr = data, *new_mc = NULL, *mc;
         int new_rev = uci->cpu_sig.rev;
         unsigned int leftover = size;
+        enum ucode_state state = UCODE_OK;
 
         while (leftover) {
                 struct microcode_header_intel mc_header;
@@ -412,11 +389,15 @@ static int generic_load_microcode(int cpu, void *data, size_t size,
                 leftover  -= mc_size;
         }
 
-        if (!new_mc)
+        if (leftover) {
+                if (new_mc)
+                        vfree(new_mc);
+                state = UCODE_ERROR;
                 goto out;
+        }
 
-        if (leftover) {
-                vfree(new_mc);
+        if (!new_mc) {
+                state = UCODE_NFOUND;
                 goto out;
         }
 
@@ -427,9 +408,8 @@ static int generic_load_microcode(int cpu, void *data, size_t size,
         pr_debug("microcode: CPU%d found a matching microcode update with"
                  " version 0x%x (current=0x%x)\n",
                         cpu, new_rev, uci->cpu_sig.rev);
-
- out:
-        return (int)leftover;
+out:
+        return state;
 }
 
 static int get_ucode_fw(void *to, const void *from, size_t n)
@@ -438,21 +418,19 @@ static int get_ucode_fw(void *to, const void *from, size_t n)
         return 0;
 }
 
-static int request_microcode_fw(int cpu, struct device *device)
+static enum ucode_state request_microcode_fw(int cpu, struct device *device)
 {
         char name[30];
         struct cpuinfo_x86 *c = &cpu_data(cpu);
         const struct firmware *firmware;
-        int ret;
+        enum ucode_state ret;
 
-        /* We should bind the task to the CPU */
-        BUG_ON(cpu != raw_smp_processor_id());
         sprintf(name, "intel-ucode/%02x-%02x-%02x",
                 c->x86, c->x86_model, c->x86_mask);
-        ret = request_firmware(&firmware, name, device);
-        if (ret) {
+
+        if (request_firmware(&firmware, name, device)) {
                 pr_debug("microcode: data file %s load failed\n", name);
-                return ret;
+                return UCODE_NFOUND;
         }
 
         ret = generic_load_microcode(cpu, (void *)firmware->data,
@@ -468,11 +446,9 @@ static int get_ucode_user(void *to, const void *from, size_t n)
         return copy_from_user(to, from, n);
 }
 
-static int request_microcode_user(int cpu, const void __user *buf, size_t size)
+static enum ucode_state
+request_microcode_user(int cpu, const void __user *buf, size_t size)
 {
-        /* We should bind the task to the CPU */
-        BUG_ON(cpu != raw_smp_processor_id());
-
         return generic_load_microcode(cpu, (void *)buf, size, &get_ucode_user);
 }