x86: EDAC: MCE: Fix MCE decoding callback logic

Make decoding of MCEs happen only on AMD hardware by registering a
non-default callback only on CPU families which support it.

While looking at the interaction of decode_mce() with the other MCE
code i also noticed a few other things and made the following
cleanups/fixes:

 - Fixed the mce_decode() weak alias - a weak alias is really not
   good here, it should be a proper callback. A weak alias will be
   overriden if a piece of code is built into the kernel - not
   good, obviously.

 - The patch initializes the callback on AMD family 10h and 11h.

 - Added the more correct fallback printk of:

	No support for human readable MCE decoding on this CPU type.
	Transcribe the message and run it through 'mcelog --ascii' to decode.

   On CPUs that dont have a decoder.

 - Made the surrounding code more readable.

Note that the callback allows us to have a default fallback -
without having to check the CPU versions during the printout
itself. When an EDAC module registers itself, it can install the
decode-print function.

(there's no unregister needed as this is core code.)

version -v2 by Borislav Petkov:

 - add K8 to the set of supported CPUs

 - always build in edac_mce_amd since we use an early_initcall now

 - fix checkpatch warnings
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andi Kleen <andi@firstfloor.org>
LKML-Reference: <20091001141432.GA11410@aftab>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/include/asm/mce.h

@@ -133,6 +133,8 @@ static inline void winchip_mcheck_init(struct cpuinfo_x86 *c) {}
 static inline void enable_p5_mce(void) {}
 #endif
 
+extern void (*x86_mce_decode_callback)(struct mce *m);
+
 void mce_setup(struct mce *m);
 void mce_log(struct mce *m);
 DECLARE_PER_CPU(struct sys_device, mce_dev);

arch/x86/kernel/cpu/mcheck/mce.c

@@ -85,6 +85,18 @@ static DECLARE_WAIT_QUEUE_HEAD(mce_wait);
 static DEFINE_PER_CPU(struct mce, mces_seen);
 static int			cpu_missing;
 
+static void default_decode_mce(struct mce *m)
+{
+	pr_emerg("No human readable MCE decoding support on this CPU type.\n");
+	pr_emerg("Run the message through 'mcelog --ascii' to decode.\n");
+}
+
+/*
+ * CPU/chipset specific EDAC code can register a callback here to print
+ * MCE errors in a human-readable form:
+ */
+void (*x86_mce_decode_callback)(struct mce *m) = default_decode_mce;
+EXPORT_SYMBOL(x86_mce_decode_callback);
 
 /* MCA banks polled by the period polling timer for corrected events */
 DEFINE_PER_CPU(mce_banks_t, mce_poll_banks) = {
@@ -165,46 +177,46 @@ void mce_log(struct mce *mce)
 	set_bit(0, &mce_need_notify);
 }
 
-void __weak decode_mce(struct mce *m)
-{
-	return;
-}
-
 static void print_mce(struct mce *m)
 {
-	printk(KERN_EMERG
-	       "CPU %d: Machine Check Exception: %16Lx Bank %d: %016Lx\n",
+	pr_emerg("CPU %d: Machine Check Exception: %16Lx Bank %d: %016Lx\n",
 	       m->extcpu, m->mcgstatus, m->bank, m->status);
+
 	if (m->ip) {
-		printk(KERN_EMERG "RIP%s %02x:<%016Lx> ",
-		       !(m->mcgstatus & MCG_STATUS_EIPV) ? " !INEXACT!" : "",
-		       m->cs, m->ip);
+		pr_emerg("RIP%s %02x:<%016Lx> ",
+			!(m->mcgstatus & MCG_STATUS_EIPV) ? " !INEXACT!" : "",
+				m->cs, m->ip);
+
 		if (m->cs == __KERNEL_CS)
 			print_symbol("{%s}", m->ip);
-		printk(KERN_CONT "\n");
+		pr_cont("\n");
 	}
-	printk(KERN_EMERG "TSC %llx ", m->tsc);
+
+	pr_emerg("TSC %llx ", m->tsc);
 	if (m->addr)
-		printk(KERN_CONT "ADDR %llx ", m->addr);
+		pr_cont("ADDR %llx ", m->addr);
 	if (m->misc)
-		printk(KERN_CONT "MISC %llx ", m->misc);
-	printk(KERN_CONT "\n");
-	printk(KERN_EMERG "PROCESSOR %u:%x TIME %llu SOCKET %u APIC %x\n",
-			m->cpuvendor, m->cpuid, m->time, m->socketid,
-			m->apicid);
+		pr_cont("MISC %llx ", m->misc);
+
+	pr_cont("\n");
+	pr_emerg("PROCESSOR %u:%x TIME %llu SOCKET %u APIC %x\n",
+		m->cpuvendor, m->cpuid, m->time, m->socketid, m->apicid);
 
-	decode_mce(m);
+	/*
+	 * Print out human-readable details about the MCE error,
+	 * (if the CPU has an implementation for that):
+	 */
+	x86_mce_decode_callback(m);
 }
 
 static void print_mce_head(void)
 {
-	printk(KERN_EMERG "\nHARDWARE ERROR\n");
+	pr_emerg("\nHARDWARE ERROR\n");
 }
 
 static void print_mce_tail(void)
 {
-	printk(KERN_EMERG "This is not a software problem!\n"
-	       "Run through mcelog --ascii to decode and contact your hardware vendor\n");
+	pr_emerg("This is not a software problem!\n");
 }
 
 #define PANIC_TIMEOUT 5 /* 5 seconds */
@@ -218,6 +230,7 @@ static atomic_t mce_fake_paniced;
 static void wait_for_panic(void)
 {
 	long timeout = PANIC_TIMEOUT*USEC_PER_SEC;
+
 	preempt_disable();
 	local_irq_enable();
 	while (timeout-- > 0)
@@ -285,6 +298,7 @@ static void mce_panic(char *msg, struct mce *final, char *exp)
 static int msr_to_offset(u32 msr)
 {
 	unsigned bank = __get_cpu_var(injectm.bank);
+
 	if (msr == rip_msr)
 		return offsetof(struct mce, ip);
 	if (msr == MSR_IA32_MCx_STATUS(bank))

drivers/edac/Makefile

@@ -18,7 +18,7 @@ edac_core-objs	+= edac_pci.o edac_pci_sysfs.o
 endif
 
 ifdef CONFIG_CPU_SUP_AMD
-edac_core-objs  += edac_mce_amd.o
+obj-$(CONFIG_X86_MCE)			+= edac_mce_amd.o
 endif
 
 obj-$(CONFIG_EDAC_AMD76X)		+= amd76x_edac.o

drivers/edac/edac_mce_amd.c

@@ -362,7 +362,7 @@ static inline void amd_decode_err_code(unsigned int ec)
 		pr_warning("Huh? Unknown MCE error 0x%x\n", ec);
 }
 
-void decode_mce(struct mce *m)
+static void amd_decode_mce(struct mce *m)
 {
 	struct err_regs regs;
 	int node, ecc;
@@ -420,3 +420,16 @@ void decode_mce(struct mce *m)
 
 	amd_decode_err_code(m->status & 0xffff);
 }
+
+static int __init mce_amd_init(void)
+{
+	/*
+	 * We can decode MCEs for Opteron and later CPUs:
+	 */
+	if ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) &&
+	    (boot_cpu_data.x86 >= 0xf))
+		x86_mce_decode_callback = amd_decode_mce;
+
+	return 0;
+}
+early_initcall(mce_amd_init);