[PATCH 0/2] Enable mce inject driver exit

[PATCH 0/2] Enable mce inject driver exit

[Fenghua Yu]

From: Fenghua Yu <fenghua.yu@intel.com>

This patch set enables mce inject driver exit. So mce inject driver can be
removed like other drivers. This makes the driver more useful in debugging mce
issues or debugging issues in the driver itself.

Fenghua Yu (2):
  x86/kernel/cpu/mcheck/mce-inject.c: Add mce inject driver exit
  x86/kernel/cpu/mcheck/mce.c: Interfaces for mce inject driver exit

 arch/x86/include/asm/mce.h              |    3 +-
 arch/x86/kernel/cpu/mcheck/mce-inject.c |   14 +++++++++--
 arch/x86/kernel/cpu/mcheck/mce.c        |   35 +++++++++++++++++++++++++++++-
 3 files changed, 46 insertions(+), 6 deletions(-)

-- 
1.7.2

[PATCH 1/2] x86/kernel/cpu/mcheck/mce-inject.c: Add mce inject driver exit

[Fenghua Yu]

From: Fenghua Yu <fenghua.yu@intel.com>

Gracefully remove mce_inject driver. This avoids rebooting machine if one wants
to release the driver. It makes the driver more useful for debugging mce issues
or debugging the driver itself. And the mce code is more clean and reasonable.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Acked-by: Tony Luck <tony.luck@intel.com>
---
 arch/x86/kernel/cpu/mcheck/mce-inject.c |   14 +++++++++++---
 1 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce-inject.c b/arch/x86/kernel/cpu/mcheck/mce-inject.c
index 0ed633c..9966a61 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-inject.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-inject.c
@@ -179,7 +179,7 @@ static void raise_mce(struct mce *m)
 }
 
 /* Error injection interface */
-static ssize_t mce_write(struct file *filp, const char __user *ubuf,
+static ssize_t mce_write_inject(struct file *filp, const char __user *ubuf,
 			 size_t usize, loff_t *off)
 {
 	struct mce m;
@@ -210,17 +210,25 @@ static ssize_t mce_write(struct file *filp, const char __user *ubuf,
 	return usize;
 }
 
-static int inject_init(void)
+static int __init inject_init(void)
 {
 	if (!alloc_cpumask_var(&mce_inject_cpumask, GFP_KERNEL))
 		return -ENOMEM;
 	printk(KERN_INFO "Machine check injector initialized\n");
-	mce_chrdev_ops.write = mce_write;
+	mce_write_register(mce_write_inject);
 	register_die_notifier(&mce_raise_nb);
 	return 0;
 }
 
+static void __exit inject_exit(void)
+{
+	mce_write_unregister();
+	unregister_die_notifier(&mce_raise_nb);
+	free_cpumask_var(mce_inject_cpumask);
+}
+
 module_init(inject_init);
+module_exit(inject_exit);
 /*
  * Cannot tolerate unloading currently because we cannot
  * guarantee all openers of mce_chrdev will get a reference to us.
-- 
1.7.2

[PATCH 2/2] x86/kernel/cpu/mcheck/mce.c: Interfaces for mce inject driver exit

[Fenghua Yu]

From: Fenghua Yu <fenghua.yu@intel.com>

Provide mce_write register and unregister interfaces for mce inject driver to
call. The interfaces take care of race condition for mce write.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Acked-by: Tony Luck <tony.luck@intel.com>
---
 arch/x86/include/asm/mce.h       |    3 ++-
 arch/x86/kernel/cpu/mcheck/mce.c |   35 +++++++++++++++++++++++++++++++++--
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index eb16e94..0b777c4 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -198,7 +198,6 @@ int mce_notify_irq(void);
 void mce_notify_process(void);
 
 DECLARE_PER_CPU(struct mce, injectm);
-extern struct file_operations mce_chrdev_ops;
 
 /*
  * Exception handler
@@ -240,5 +239,7 @@ struct cper_sec_mem_err;
 extern void apei_mce_report_mem_error(int corrected,
 				      struct cper_sec_mem_err *mem_err);
 
+extern void mce_write_register(void *mce_write_inject);
+extern void mce_write_unregister(void);
 #endif /* __KERNEL__ */
 #endif /* _ASM_X86_MCE_H */
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 3385ea2..9f0bbcc 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -50,6 +50,7 @@
 #include "mce-internal.h"
 
 static DEFINE_MUTEX(mce_read_mutex);
+static DEFINE_MUTEX(mce_write_mutex);
 
 #define rcu_dereference_check_mce(p) \
 	rcu_dereference_index_check((p), \
@@ -1539,6 +1540,36 @@ static int __mce_read_apei(char __user **ubuf, size_t usize)
 	return 0;
 }
 
+static ssize_t (*_mce_write)(struct file *filp, const char __user *ubuf,
+			 size_t usize, loff_t *off);
+void mce_write_register(void *mce_write_inject)
+{
+	mutex_lock(&mce_write_mutex);
+	_mce_write = mce_write_inject;
+	mutex_unlock(&mce_write_mutex);
+}
+EXPORT_SYMBOL(mce_write_register);
+
+void mce_write_unregister(void)
+{
+	mutex_lock(&mce_write_mutex);
+	_mce_write = 0;
+	mutex_unlock(&mce_write_mutex);
+}
+EXPORT_SYMBOL(mce_write_unregister);
+
+static ssize_t mce_write(struct file *filp, const char __user *ubuf,
+			 size_t usize, loff_t *off)
+{
+	ssize_t ret = 0;
+
+	mutex_lock(&mce_write_mutex);
+	if (_mce_write)
+		ret = _mce_write(filp, ubuf, usize, off);
+	mutex_unlock(&mce_write_mutex);
+	return ret;
+}
+
 static ssize_t mce_read(struct file *filp, char __user *ubuf, size_t usize,
 			loff_t *off)
 {
@@ -1659,11 +1690,11 @@ static long mce_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
 	}
 }
 
-/* Modified in mce-inject.c, so not static or const */
-struct file_operations mce_chrdev_ops = {
+static const struct file_operations mce_chrdev_ops = {
 	.open			= mce_open,
 	.release		= mce_release,
 	.read			= mce_read,
+	.write			= mce_write,
 	.poll			= mce_poll,
 	.unlocked_ioctl		= mce_ioctl,
 	.llseek		= no_llseek,
-- 
1.7.2