powerpc/64s/pseries: Add ERAT specific machine check handler

Don't treat ERAT MCEs as SLB, don't save the SLB and use a specific
ERAT flush to recover it.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201128070728.825934-7-npiggin@gmail.com

arch/powerpc/include/asm/mce.h

@@ -228,6 +228,7 @@ int mce_register_notifier(struct notifier_block *nb);
 int mce_unregister_notifier(struct notifier_block *nb);
 #ifdef CONFIG_PPC_BOOK3S_64
 void flush_and_reload_slb(void);
+void flush_erat(void);
 long __machine_check_early_realmode_p7(struct pt_regs *regs);
 long __machine_check_early_realmode_p8(struct pt_regs *regs);
 long __machine_check_early_realmode_p9(struct pt_regs *regs);

arch/powerpc/kernel/mce_power.c

@@ -97,7 +97,7 @@ void flush_and_reload_slb(void)
 }
 #endif
 
-static void flush_erat(void)
+void flush_erat(void)
 {
 #ifdef CONFIG_PPC_BOOK3S_64
 	if (!early_cpu_has_feature(CPU_FTR_ARCH_300)) {

arch/powerpc/platforms/pseries/ras.c

@@ -526,8 +526,11 @@ static int mce_handle_err_realmode(int disposition, u8 error_type)
 #ifdef CONFIG_PPC_BOOK3S_64
 	if (disposition == RTAS_DISP_NOT_RECOVERED) {
 		switch (error_type) {
-		case	MC_ERROR_TYPE_SLB:
 		case	MC_ERROR_TYPE_ERAT:
+			flush_erat();
+			disposition = RTAS_DISP_FULLY_RECOVERED;
+			break;
+		case	MC_ERROR_TYPE_SLB:
 			/*
 			 * Store the old slb content in paca before flushing.
 			 * Print this when we go to virtual mode.