Merge branch 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa...

[karo-tx-linux.git] / arch / powerpc / kernel / exceptions-64s.S

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 9029afd1fa2ab2ce231045659abf11ec9eaa32f6..f14f3c04ec7e0c7d366f60d161ff0ced6f1497ad 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -1325,10 +1325,18 @@ EXC_VIRT_NONE(0x5800, 0x100)
        std     r10,PACA_EXGEN+EX_R13(r13);             \
        EXCEPTION_PROLOG_PSERIES_1(soft_nmi_common, _H)
 
+/*
+ * Branch to soft_nmi_interrupt using the emergency stack. The emergency
+ * stack is one that is usable by maskable interrupts so long as MSR_EE
+ * remains off. It is used for recovery when something has corrupted the
+ * normal kernel stack, for example. The "soft NMI" must not use the process
+ * stack because we want irq disabled sections to avoid touching the stack
+ * at all (other than PMU interrupts), so use the emergency stack for this,
+ * and run it entirely with interrupts hard disabled.
+ */
 EXC_COMMON_BEGIN(soft_nmi_common)
        mr      r10,r1
        ld      r1,PACAEMERGSP(r13)
-       ld      r1,PACA_NMI_EMERG_SP(r13)
        subi    r1,r1,INT_FRAME_SIZE
        EXCEPTION_COMMON_NORET_STACK(PACA_EXGEN, 0x900,
                        system_reset, soft_nmi_interrupt,