x86/nmi, EDAC: Get rid of DRAM error reporting thru PCI SERR NMI

Apparently, some machines used to report DRAM errors through a PCI SERR
NMI. This is why we have a call into EDAC in the NMI handler. See

  c0d121720220 ("drivers/edac: add new nmi rescan").

From looking at the patch above, that's two drivers: e752x_edac.c and
e7xxx_edac.c. Now, I wanna say those are old machines which are probably
decommissioned already.

Tony says that "[t]the newest CPU supported by either of those drivers
is the Xeon E7520 (a.k.a. "Nehalem") released in Q1'2010. Possibly some
folks are still using these ... but people that hold onto h/w for 7
years generally cling to old s/w too ... so I'd guess it unlikely that
we will get complaints for breaking these in upstream."

So even if there is a small number still in use, we did load EDAC with
edac_op_state == EDAC_OPSTATE_POLL by default (we still do, in fact)
which means a default EDAC setup without any parameters supplied on the
command line or otherwise would never even log the error in the NMI
handler because we're polling by default:

  inline int edac_handler_set(void)
  {
         if (edac_op_state == EDAC_OPSTATE_POLL)
                 return 0;

         return atomic_read(&edac_handlers);
  }

So, long story short, I'd like to get rid of that nastiness called
edac_stub.c and confine all the EDAC drivers solely to drivers/edac/. If
we ever have to do stuff like that again, it should be notifiers we're
using and not some insanity like this one.

Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>

arch/x86/kernel/nmi.c

@@ -224,17 +224,6 @@ pci_serr_error(unsigned char reason, struct pt_regs *regs)
 	pr_emerg("NMI: PCI system error (SERR) for reason %02x on CPU %d.\n",
 		 reason, smp_processor_id());
 
-	/*
-	 * On some machines, PCI SERR line is used to report memory
-	 * errors. EDAC makes use of it.
-	 */
-#if defined(CONFIG_EDAC)
-	if (edac_handler_set()) {
-		edac_atomic_assert_error();
-		return;
-	}
-#endif
-
 	if (panic_on_unrecovered_nmi)
 		nmi_panic(regs, "NMI: Not continuing");
 

drivers/edac/edac_stub.c

@@ -44,25 +44,3 @@ static int __init edac_report_setup(char *str)
 	return 0;
 }
 __setup("edac_report=", edac_report_setup);
-
-/*
- * called to determine if there is an EDAC driver interested in
- * knowing an event (such as NMI) occurred
- */
-int edac_handler_set(void)
-{
-	if (edac_op_state == EDAC_OPSTATE_POLL)
-		return 0;
-
-	return atomic_read(&edac_handlers);
-}
-EXPORT_SYMBOL_GPL(edac_handler_set);
-
-/*
- * handler for NMI type of interrupts to assert error
- */
-void edac_atomic_assert_error(void)
-{
-	edac_err_assert++;
-}
-EXPORT_SYMBOL_GPL(edac_atomic_assert_error);

include/linux/edac.h

@@ -31,8 +31,6 @@ extern int edac_op_state;
 extern int edac_err_assert;
 extern atomic_t edac_handlers;
 
-extern int edac_handler_set(void);
-extern void edac_atomic_assert_error(void);
 extern struct bus_type *edac_get_sysfs_subsys(void);
 
 enum {