x86-microcode: get rid of set_cpus_allowed()

From: Dmitry Adamushko
Date: Mon Mar 09 2009 - 15:39:21 EST


Hi,


here is a possible candidate for Rusty's cpumask-refactored series.
Note the [*] remark below though.

---


From: Dmitry Adamushko <dmitry.adamushko@xxxxxxxxx>

Subject: x86-microcode: get rid of set_cpus_allowed()

- Get rid of set_cpus_allowed() in the generic 'microcode_core' part and
instead use either smp_call_function_single() or {rd,wr}msr_on_cpu()
in the cpu-specific parts [*];

That said, if need be, the 'struct microcode_ops' callbacks must ensure that
they run on a target cpu.

- Cleanup of the synchronization logic in the 'microcode_core' part

The generic 'microcode_core' part guarantees that only a single cpu is being
updated at any particular moment of time.


[*] regarding the (ugly) call-sites marked with "Sigh, smp_call_function_single() gets upset when called..."

The problem is that smp_call_function_single() does

/* Can deadlock when called with interrupts disabled */
WARN_ON(irqs_disabled());

even when (cpu == me) [ for the sake of consistency as I can imagine ]

The warning is harmless in our case (only cpu#0 is running at this point
so this is the "cpu == me" case for smp_call_function_single()) and
originates from the following path:

(suspend_enter() runs with interrupts disabled)

suspend_enter() -> device_power_up() -> ... -> mc_sysdev_resume() ->
microcode_init_cpu(0)

It does make this code look ugly though :-(


Signed-off-by: Dmitry Adamushko <dmitry.adamushko@xxxxxxxxx>
CC: Andreas Herrmann <andreas.herrmann3@xxxxxxx>
CC: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxx>

---

diff --git a/arch/x86/kernel/microcode_amd.c b/arch/x86/kernel/microcode_amd.c
index c25fdb3..ff98c97 100644
--- a/arch/x86/kernel/microcode_amd.c
+++ b/arch/x86/kernel/microcode_amd.c
@@ -80,15 +80,13 @@ 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)
{
struct cpuinfo_x86 *c = &cpu_data(cpu);
u32 dummy;
+ int ret = 0;

memset(csig, 0, sizeof(*csig));
if (c->x86_vendor != X86_VENDOR_AMD || c->x86 < 0x10) {
@@ -96,9 +94,19 @@ static int collect_cpu_info_amd(int cpu, struct cpu_signature *csig)
"supported\n", cpu, c->x86);
return -1;
}
- rdmsr(MSR_AMD64_PATCH_LEVEL, csig->rev, dummy);
+
+ /*
+ * Sigh, smp_call_function_single() gets upset when called with irqs disabled,
+ * but it's OK for the mc_sysdev_resume() (cpu == 0) case.
+ */
+ if (raw_smp_processor_id() == cpu)
+ rdmsr(MSR_AMD64_PATCH_LEVEL, csig->rev, dummy);
+ else
+ ret = rdmsr_on_cpu(cpu, MSR_AMD64_PATCH_LEVEL, &csig->rev, &dummy);
+
printk(KERN_INFO "microcode: CPU%d: patch_level=0x%x\n", cpu, csig->rev);
- return 0;
+
+ return ret;
}

static int get_matching_microcode(int cpu, void *mc, int rev)
@@ -145,37 +153,54 @@ static int get_matching_microcode(int cpu, void *mc, int rev)
return 1;
}

+struct ucode_am_info {
+ unsigned long data_code;
+ u32 rev;
+};
+
+static void __apply_microcode_amd(void *info)
+{
+ struct ucode_am_info *mi = info;
+ u32 dummy;
+
+ wrmsrl(MSR_AMD64_PATCH_LOADER, mi->data_code);
+ /* get patch id after patching */
+ rdmsr(MSR_AMD64_PATCH_LEVEL, mi->rev, dummy);
+}
+
static void 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;
+ struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
struct microcode_amd *mc_amd = uci->mc;
-
- /* We should bind the task to the CPU */
- BUG_ON(cpu_num != cpu);
+ struct ucode_am_info mi;
+ int ret = 0;

if (mc_amd == NULL)
return;

- 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);
+ memset(&mi, 0, sizeof(mi));
+ mi.data_code = (unsigned long)&mc_amd->hdr.data_code;
+
+ /*
+ * Sigh, smp_call_function_single() gets upset when called with irqs disabled,
+ * but it's OK for the mc_sysdev_resume() (cpu == 0) case.
+ */
+ if (raw_smp_processor_id() == cpu)
+ __apply_microcode_amd(&mi);
+ else
+ ret = smp_call_function_single(cpu, __apply_microcode_amd, &mi, 1);

/* check current patch id and patch's id for match */
- if (rev != mc_amd->hdr.patch_id) {
+ if (ret || mi.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;
}

printk(KERN_INFO "microcode: CPU%d: updated (new patch_level=0x%x)\n",
- cpu, rev);
+ cpu, mi.rev);

- uci->cpu_sig.rev = rev;
+ uci->cpu_sig.rev = mi.rev;
}

static int get_ucode_data(void *to, const u8 *from, size_t n)
@@ -329,9 +354,6 @@ static int request_microcode_fw(int cpu, struct device *device)
const struct firmware *firmware;
int ret;

- /* We should bind the task to the CPU */
- BUG_ON(cpu != raw_smp_processor_id());
-
ret = request_firmware(&firmware, fw_name, device);
if (ret) {
printk(KERN_ERR "microcode: failed to load file %s\n", fw_name);
diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
index c9b721b..caaa2e6 100644
--- a/arch/x86/kernel/microcode_core.c
+++ b/arch/x86/kernel/microcode_core.c
@@ -101,7 +101,15 @@ 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.
+ */
static DEFINE_MUTEX(microcode_mutex);

struct ucode_cpu_info ucode_cpu_info[NR_CPUS];
@@ -110,19 +118,15 @@ EXPORT_SYMBOL_GPL(ucode_cpu_info);
#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;

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;
@@ -130,7 +134,6 @@ static int do_microcode_update(const void __user *buf, size_t size)
microcode_ops->apply_microcode(cpu);
}
out:
- set_cpus_allowed_ptr(current, &old);
return error;
}

@@ -218,11 +221,8 @@ static ssize_t reload_store(struct sys_device *dev,
if (end == buf)
return -EINVAL;
if (val == 1) {
- cpumask_t old = current->cpus_allowed;
-
get_online_cpus();
if (cpu_online(cpu)) {
- set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
mutex_lock(&microcode_mutex);
if (uci->valid) {
err = microcode_ops->request_microcode_fw(cpu,
@@ -231,7 +231,6 @@ static ssize_t reload_store(struct sys_device *dev,
microcode_ops->apply_microcode(cpu);
}
mutex_unlock(&microcode_mutex);
- set_cpus_allowed_ptr(current, &old);
}
put_online_cpus();
}
@@ -272,7 +271,7 @@ static struct attribute_group mc_attr_group = {
.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;

@@ -280,13 +279,6 @@ 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)
{
struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
@@ -311,14 +303,14 @@ static int microcode_resume_cpu(int cpu)
* to this cpu (a bit of paranoia):
*/
if (microcode_ops->collect_cpu_info(cpu, &nsig)) {
- __microcode_fini_cpu(cpu);
+ microcode_fini_cpu(cpu);
printk(KERN_ERR "failed to collect_cpu_info for resuming cpu #%d\n",
cpu);
return -1;
}

if ((nsig.sig != uci->cpu_sig.sig) || (nsig.pf != uci->cpu_sig.pf)) {
- __microcode_fini_cpu(cpu);
+ 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? */
@@ -328,7 +320,7 @@ static int microcode_resume_cpu(int cpu)
return 0;
}

-static void microcode_update_cpu(int cpu)
+static void microcode_init_cpu(int cpu)
{
struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
int err = 0;
@@ -349,21 +341,6 @@ static void microcode_update_cpu(int cpu)
microcode_ops->apply_microcode(cpu);
}

-static void microcode_init_cpu(int cpu)
-{
- cpumask_t old = current->cpus_allowed;
-
- set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
- /* We should bind the task to the CPU */
- BUG_ON(raw_smp_processor_id() != cpu);
-
- mutex_lock(&microcode_mutex);
- microcode_update_cpu(cpu);
- mutex_unlock(&microcode_mutex);
-
- set_cpus_allowed_ptr(current, &old);
-}
-
static int mc_sysdev_add(struct sys_device *sys_dev)
{
int err, cpu = sys_dev->id;
@@ -403,8 +380,16 @@ static int mc_sysdev_resume(struct sys_device *dev)
if (!cpu_online(cpu))
return 0;

- /* only CPU 0 will apply ucode here */
- microcode_update_cpu(0);
+ /*
+ * 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);
+
+ microcode_init_cpu(cpu);
return 0;
}

@@ -477,8 +462,13 @@ 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);
@@ -502,7 +492,11 @@ 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);
diff --git a/arch/x86/kernel/microcode_intel.c b/arch/x86/kernel/microcode_intel.c
index b7f4c92..9dc21dc 100644
--- a/arch/x86/kernel/microcode_intel.c
+++ b/arch/x86/kernel/microcode_intel.c
@@ -74,7 +74,7 @@
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/sched.h>
-#include <linux/smp_lock.h>
+#include <linux/smp.h>
#include <linux/cpumask.h>
#include <linux/module.h>
#include <linux/slab.h>
@@ -149,46 +149,64 @@ 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);
+struct ucode_cc_info {
+ struct cpu_signature *csig;
+ int do_pf;
+};

-static int collect_cpu_info(int cpu_num, struct cpu_signature *csig)
+static void __collect_cpu_info(void *info)
{
- struct cpuinfo_x86 *c = &cpu_data(cpu_num);
- unsigned long flags;
+ struct ucode_cc_info *cc = info;
unsigned int val[2];

+ if (cc->do_pf) {
+ /* get processor flags from MSR 0x17 */
+ rdmsr(MSR_IA32_PLATFORM_ID, val[0], val[1]);
+ cc->csig->pf = 1 << ((val[1] >> 18) & 7);
+ }
+
+ wrmsrl(MSR_IA32_UCODE_REV, 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], cc->csig->rev);
+}
+
+static int collect_cpu_info(int cpu, struct cpu_signature *csig)
+{
+ struct cpuinfo_x86 *c = &cpu_data(cpu);
+ struct ucode_cc_info cc;
+ int ret = 0;
+
memset(csig, 0, sizeof(*csig));

if (c->x86_vendor != X86_VENDOR_INTEL || c->x86 < 6 ||
cpu_has(c, X86_FEATURE_IA64)) {
printk(KERN_ERR "microcode: CPU%d not a capable Intel "
- "processor\n", cpu_num);
+ "processor\n", cpu);
return -1;
}

csig->sig = cpuid_eax(0x00000001);

- if ((c->x86_model >= 5) || (c->x86 > 6)) {
- /* get processor flags from MSR 0x17 */
- rdmsr(MSR_IA32_PLATFORM_ID, val[0], val[1]);
- csig->pf = 1 << ((val[1] >> 18) & 7);
- }
+ cc.do_pf = 0;
+ cc.csig = csig;
+ if ((c->x86_model >= 5) || (c->x86 > 6))
+ cc.do_pf = 1;

- /* 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);
+ /*
+ * Sigh, smp_call_function_single() gets upset when called with irqs disabled,
+ * but it's OK for the mc_sysdev_resume() (cpu == 0) case.
+ */
+ if (raw_smp_processor_id() == cpu)
+ __collect_cpu_info(&cc);
+ else
+ ret = smp_call_function_single(cpu, __collect_cpu_info, &cc, 1);

pr_debug("microcode: collect_cpu_info : sig=0x%x, pf=0x%x, rev=0x%x\n",
csig->sig, csig->pf, csig->rev);

- return 0;
+ return ret;
}

static inline int update_match_cpu(struct cpu_signature *csig, int sig, int pf)
@@ -316,48 +334,59 @@ get_matching_microcode(struct cpu_signature *cpu_sig, void *mc, int rev)
return 0;
}

-static void apply_microcode(int cpu)
-{
- unsigned long flags;
+struct ucode_am_info {
+ unsigned long bits;
unsigned int val[2];
- int cpu_num = raw_smp_processor_id();
- struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
- struct microcode_intel *mc_intel = uci->mc;
-
- /* We should bind the task to the 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);
+static void __apply_microcode(void *info)
+{
+ struct ucode_am_info *mi = info;

/* write microcode via MSR 0x79 */
- wrmsr(MSR_IA32_UCODE_WRITE,
- (unsigned long) mc_intel->bits,
- (unsigned long) mc_intel->bits >> 16 >> 16);
- wrmsr(MSR_IA32_UCODE_REV, 0, 0);
+ wrmsrl(MSR_IA32_UCODE_WRITE, mi->bits);
+ wrmsrl(MSR_IA32_UCODE_REV, 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]);
+ rdmsr(MSR_IA32_UCODE_REV, mi->val[0], mi->val[1]);
+}

- spin_unlock_irqrestore(&microcode_update_lock, flags);
- if (val[1] != mc_intel->hdr.rev) {
+static void apply_microcode(int cpu)
+{
+ struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
+ struct microcode_intel *mc_intel = uci->mc;
+ struct ucode_am_info mi;
+ int ret = 0;
+
+ if (mc_intel == NULL)
+ return;
+
+ mi.bits = (unsigned long)mc_intel->bits;
+
+ /*
+ * Sigh, smp_call_function_single() gets upset when called with irqs disabled,
+ * but it's OK for the mc_sysdev_resume() (cpu == 0) case.
+ */
+ if (raw_smp_processor_id() == cpu)
+ __apply_microcode(&mi);
+ else
+ ret = smp_call_function_single(cpu, __apply_microcode, &mi, 1);
+
+ if (ret || mi.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]);
+ "0x%x to 0x%x failed\n", cpu, uci->cpu_sig.rev, mi.val[1]);
return;
}
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],
+ cpu, uci->cpu_sig.rev, mi.val[1],
mc_intel->hdr.date & 0xffff,
mc_intel->hdr.date >> 24,
(mc_intel->hdr.date >> 16) & 0xff);
- uci->cpu_sig.rev = val[1];
+ uci->cpu_sig.rev = mi.val[1];
}

static int generic_load_microcode(int cpu, void *data, size_t size,
@@ -432,8 +461,6 @@ static int request_microcode_fw(int cpu, struct device *device)
const struct firmware *firmware;
int 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);
@@ -457,9 +484,6 @@ static int get_ucode_user(void *to, const void *from, size_t n)

static int 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);
}



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