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authorNicholas Piggin <npiggin@gmail.com>2016-12-19 19:30:05 +0100
committerMichael Ellerman <mpe@ellerman.id.au>2017-04-28 13:02:25 +0200
commitc4f3b52ce7b16824befb16ab3d045c891b08b7db (patch)
tree92f77ba25144dbe046368583e18e21c83015e642 /arch
parentpowerpc/64s: Fix system reset vs general interrupt reentrancy (diff)
downloadlinux-c4f3b52ce7b16824befb16ab3d045c891b08b7db.tar.xz
linux-c4f3b52ce7b16824befb16ab3d045c891b08b7db.zip
powerpc/64s: Disallow system reset vs system reset reentrancy
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>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/include/asm/exception-64s.h6
-rw-r--r--arch/powerpc/include/asm/paca.h5
-rw-r--r--arch/powerpc/kernel/asm-offsets.c1
-rw-r--r--arch/powerpc/kernel/exceptions-64s.S37
-rw-r--r--arch/powerpc/kernel/traps.c8
-rw-r--r--arch/powerpc/xmon/xmon.c1
6 files changed, 51 insertions, 7 deletions
diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 63a309a432ad..59134ebd7d49 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -275,6 +275,12 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
#endif
+/* Do not enable RI */
+#define EXCEPTION_PROLOG_PSERIES_NORI(area, label, h, extra, vec) \
+ EXCEPTION_PROLOG_0(area); \
+ EXCEPTION_PROLOG_1(area, extra, vec); \
+ EXCEPTION_PROLOG_PSERIES_1_NORI(label, h);
+
#define __KVM_HANDLER(area, h, n) \
BEGIN_FTR_SECTION_NESTED(947) \
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index 601e2327dd8c..b1197c1affac 100644
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -187,12 +187,15 @@ struct paca_struct {
#ifdef CONFIG_PPC_BOOK3S_64
/* Exclusive emergency stack pointer for machine check exception. */
void *mc_emergency_sp;
+
+ u16 in_nmi; /* In nmi handler */
+
/*
* Flag to check whether we are in machine check early handler
* and already using emergency stack.
*/
u16 in_mce;
- u8 hmi_event_available; /* HMI event is available */
+ u8 hmi_event_available; /* HMI event is available */
#endif
/* Stuff for accurate time accounting */
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 46732ee70b43..1466e96d36cf 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -235,6 +235,7 @@ int main(void)
#ifdef CONFIG_PPC_BOOK3S_64
OFFSET(PACAMCEMERGSP, paca_struct, mc_emergency_sp);
OFFSET(PACA_IN_MCE, paca_struct, in_mce);
+ OFFSET(PACA_IN_NMI, paca_struct, in_nmi);
#endif
OFFSET(PACAHWCPUID, paca_struct, hw_cpu_id);
OFFSET(PACAKEXECSTATE, paca_struct, kexec_state);
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 3a654b1f24e9..4be62568fbc2 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -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 */
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 76f6045b021b..2393d3c46236 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -282,11 +282,17 @@ void system_reset_exception(struct pt_regs *regs)
/* See if any machine dependent calls */
if (ppc_md.system_reset_exception) {
if (ppc_md.system_reset_exception(regs))
- return;
+ goto out;
}
die("System Reset", regs, SIGABRT);
+out:
+#ifdef CONFIG_PPC_BOOK3S_64
+ BUG_ON(get_paca()->in_nmi == 0);
+ if (get_paca()->in_nmi > 1)
+ panic("Unrecoverable nested System Reset");
+#endif
/* Must die if the interrupt is not recoverable */
if (!(regs->msr & MSR_RI))
panic("Unrecoverable System Reset");
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 2b21e90fff8d..99348a2961b8 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -2236,6 +2236,7 @@ static void dump_one_paca(int cpu)
DUMP(p, emergency_sp, "p");
#ifdef CONFIG_PPC_BOOK3S_64
DUMP(p, mc_emergency_sp, "p");
+ DUMP(p, in_nmi, "x");
DUMP(p, in_mce, "x");
DUMP(p, hmi_event_available, "x");
#endif