x86, mce: CE in last bank prevents panic by unknown MCE

[safe/jmp/linux-2.6] / arch / x86 / kernel / cpu / mcheck / mce.c

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 9c7419e..325559d 100644 (file)
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -204,6 +204,9 @@ static void print_mce_tail(void)
 
 static atomic_t mce_paniced;
 
+static int fake_panic;
+static atomic_t mce_fake_paniced;
+
 /* Panic in progress. Enable interrupts and wait for final IPI */
 static void wait_for_panic(void)
 {
@@ -221,15 +224,21 @@ static void mce_panic(char *msg, struct mce *final, char *exp)
 {
        int i;
 
-       /*
-        * Make sure only one CPU runs in machine check panic
-        */
-       if (atomic_inc_return(&mce_paniced) > 1)
-               wait_for_panic();
-       barrier();
+       if (!fake_panic) {
+               /*
+                * Make sure only one CPU runs in machine check panic
+                */
+               if (atomic_inc_return(&mce_paniced) > 1)
+                       wait_for_panic();
+               barrier();
 
-       bust_spinlocks(1);
-       console_verbose();
+               bust_spinlocks(1);
+               console_verbose();
+       } else {
+               /* Don't log too much for fake panic */
+               if (atomic_inc_return(&mce_fake_paniced) > 1)
+                       return;
+       }
        print_mce_head();
        /* First print corrected ones that are still unlogged */
        for (i = 0; i < MCE_LOG_LEN; i++) {
@@ -256,9 +265,12 @@ static void mce_panic(char *msg, struct mce *final, char *exp)
        print_mce_tail();
        if (exp)
                printk(KERN_EMERG "Machine check: %s\n", exp);
-       if (panic_timeout == 0)
-               panic_timeout = mce_panic_timeout;
-       panic(msg);
+       if (!fake_panic) {
+               if (panic_timeout == 0)
+                       panic_timeout = mce_panic_timeout;
+               panic(msg);
+       } else
+               printk(KERN_EMERG "Fake kernel panic: %s\n", msg);
 }
 
 /* Support code for software error injection */
@@ -600,7 +612,7 @@ out:
  * This way we prevent any potential data corruption in a unrecoverable case
  * and also makes sure always all CPU's errors are examined.
  *
- * Also this detects the case of an machine check event coming from outer
+ * Also this detects the case of a machine check event coming from outer
  * space (not detected by any CPUs) In this case some external agent wants
  * us to shut down, so panic too.
  *
@@ -653,7 +665,7 @@ static void mce_reign(void)
         * No machine check event found. Must be some external
         * source or one CPU is hung. Panic.
         */
-       if (!m && tolerant < 3)
+       if (global_worst <= MCE_KEEP_SEVERITY && tolerant < 3)
                mce_panic("Machine check from unknown source", NULL, NULL);
 
        /*
@@ -877,11 +889,11 @@ void do_machine_check(struct pt_regs *regs, long error_code)
        mce_setup(&m);
 
        m.mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS);
-       no_way_out = mce_no_way_out(&m, &msg);
-
        final = &__get_cpu_var(mces_seen);
        *final = m;
 
+       no_way_out = mce_no_way_out(&m, &msg);
+
        barrier();
 
        /*
@@ -2015,4 +2027,45 @@ struct dentry *mce_get_debugfs_dir(void)
 
        return dmce;
 }
+
+static void mce_reset(void)
+{
+       cpu_missing = 0;
+       atomic_set(&mce_fake_paniced, 0);
+       atomic_set(&mce_executing, 0);
+       atomic_set(&mce_callin, 0);
+       atomic_set(&global_nwo, 0);
+}
+
+static int fake_panic_get(void *data, u64 *val)
+{
+       *val = fake_panic;
+       return 0;
+}
+
+static int fake_panic_set(void *data, u64 val)
+{
+       mce_reset();
+       fake_panic = val;
+       return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fake_panic_fops, fake_panic_get,
+                       fake_panic_set, "%llu\n");
+
+static int __init mce_debugfs_init(void)
+{
+       struct dentry *dmce, *ffake_panic;
+
+       dmce = mce_get_debugfs_dir();
+       if (!dmce)
+               return -ENOMEM;
+       ffake_panic = debugfs_create_file("fake_panic", 0444, dmce, NULL,
+                                         &fake_panic_fops);
+       if (!ffake_panic)
+               return -ENOMEM;
+
+       return 0;
+}
+late_initcall(mce_debugfs_init);
 #endif