powerpc/64s: Fix system reset vs general interrupt reentrancy
The system reset interrupt can occur when MSR_EE=0, and it currently
uses the PACA_EXGEN save area.
Some PACA_EXGEN interrupts have a window where MSR_RI=1 and MSR_EE=0
when the save area is still in use. A system reset interrupt in this
window can lead to undetected corruption when the save area gets
overwritten.
This patch introduces PACA_EXNMI save area for system reset exceptions,
which closes this corruption window. It's also helpful to retain the
EXGEN state for debugging situations, even if not considering the
recoverability aspect.
This patch also moves the PACA_EXMC area down to a less frequently used
part of the paca with the new save area.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 229f22a..63a309a 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -549,8 +549,8 @@ BEGIN_FTR_SECTION \
beql ppc64_runlatch_on_trampoline; \
END_FTR_SECTION_IFSET(CPU_FTR_CTRL)
-#define EXCEPTION_COMMON(trap, label, hdlr, ret, additions) \
- EXCEPTION_PROLOG_COMMON(trap, PACA_EXGEN); \
+#define EXCEPTION_COMMON(area, trap, label, hdlr, ret, additions) \
+ EXCEPTION_PROLOG_COMMON(trap, area); \
/* Volatile regs are potentially clobbered here */ \
additions; \
addi r3,r1,STACK_FRAME_OVERHEAD; \
@@ -558,17 +558,17 @@ END_FTR_SECTION_IFSET(CPU_FTR_CTRL)
b ret
#define STD_EXCEPTION_COMMON(trap, label, hdlr) \
- EXCEPTION_COMMON(trap, label, hdlr, ret_from_except, \
- ADD_NVGPRS;ADD_RECONCILE)
+ EXCEPTION_COMMON(PACA_EXGEN, trap, label, hdlr, \
+ ret_from_except, ADD_NVGPRS;ADD_RECONCILE)
/*
* Like STD_EXCEPTION_COMMON, but for exceptions that can occur
* in the idle task and therefore need the special idle handling
* (finish nap and runlatch)
*/
-#define STD_EXCEPTION_COMMON_ASYNC(trap, label, hdlr) \
- EXCEPTION_COMMON(trap, label, hdlr, ret_from_except_lite, \
- FINISH_NAP;ADD_RECONCILE;RUNLATCH_ON)
+#define STD_EXCEPTION_COMMON_ASYNC(trap, label, hdlr) \
+ EXCEPTION_COMMON(PACA_EXGEN, trap, label, hdlr, \
+ ret_from_except_lite, FINISH_NAP;ADD_RECONCILE;RUNLATCH_ON)
/*
* When the idle code in power4_idle puts the CPU into NAP mode,