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

[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 3a654b1f24e9b00256c71d0f3ad9257cbe6979ae..4be62568fbc27b5700bc694679ab22fa1a2f5f11 100644 (file)
--- 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 */