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powerpc/64s: Disallow system reset vs system reset reentrancy

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In preparation for using a dedicated stack for system reset interrupts,
prevent a nested system reset from recovering, in order to simplify
code that is called in crash/debug path. This allows a system reset
interrupt to just use the base stack pointer.

Keep an in_nmi nesting counter similarly to the in_mce counter. Consider
the interrrupt non-recoverable if it is taken inside another system
reset.

Interrupt nesting could be allowed similarly to MCE, but system reset
is a special case that's not for normal operation, so simplicity wins
until there is requirement for nested system reset interrupts.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin
2016-12-20 04:30:05 +10:00
committed by Michael Ellerman
parent a3d96f70c1
commit c4f3b52ce7
6 changed files with 51 additions and 7 deletions
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37
arch/powerpc/kernel/exceptions-64s.S
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@@ -116,7 +116,11 @@ EXC_VIRT_NONE(0x4000, 0x100)
EXC_REAL_BEGIN(system_reset, 0x100, 0x100)
SET_SCRATCH0(r13)
EXCEPTION_PROLOG_PSERIES(PACA_EXNMI, system_reset_common, EXC_STD,
/*
* MSR_RI is not enabled, because PACA_EXNMI and nmi stack is
* being used, so a nested NMI exception would corrupt it.
*/
EXCEPTION_PROLOG_PSERIES_NORI(PACA_EXNMI, system_reset_common, EXC_STD,
IDLETEST, 0x100)
EXC_REAL_END(system_reset, 0x100, 0x100)
@@ -128,9 +132,31 @@ EXC_COMMON_BEGIN(system_reset_idle_common)
#endif
EXC_COMMON_BEGIN(system_reset_common)
/*
* Increment paca->in_nmi then enable MSR_RI. SLB or MCE will be able
* to recover, but nested NMI will notice in_nmi and not recover
* because of the use of the NMI stack. in_nmi reentrancy is tested in
* system_reset_exception.
*/
lhz r10,PACA_IN_NMI(r13)
addi r10,r10,1
sth r10,PACA_IN_NMI(r13)
li r10,MSR_RI
mtmsrd r10,1
EXCEPTION_COMMON(PACA_EXNMI, 0x100,
system_reset, system_reset_exception,
ret_from_except, ADD_NVGPRS;ADD_RECONCILE)
system_reset, system_reset_exception, 1f,
ADD_NVGPRS;ADD_RECONCILE)
1: /* EXCEPTION_COMMON continues here */
/*
* The stack is no longer in use, decrement in_nmi.
*/
lhz r10,PACA_IN_NMI(r13)
subi r10,r10,1
sth r10,PACA_IN_NMI(r13)
b ret_from_except
#ifdef CONFIG_PPC_PSERIES
/*
@@ -138,8 +164,9 @@ EXC_COMMON_BEGIN(system_reset_common)
*/
TRAMP_REAL_BEGIN(system_reset_fwnmi)
SET_SCRATCH0(r13) /* save r13 */
EXCEPTION_PROLOG_PSERIES(PACA_EXNMI, system_reset_common, EXC_STD,
NOTEST, 0x100)
/* See comment at system_reset exception */
EXCEPTION_PROLOG_PSERIES_NORI(PACA_EXNMI, system_reset_common,
EXC_STD, NOTEST, 0x100)
#endif /* CONFIG_PPC_PSERIES */