1 files changed, 33 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index e16eb2a33173..6ff3cf506088 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -191,6 +191,37 @@ exception_marker:
         ori     reg,reg,(label)@l;      /* virt addr of handler ... */
 #endif
 
+/*
+ * Equal to EXCEPTION_PROLOG_PSERIES, except that it forces 64bit mode.
+ * The firmware calls the registered system_reset_fwnmi and
+ * machine_check_fwnmi handlers in 32bit mode if the cpu happens to run
+ * a 32bit application at the time of the event.
+ * This firmware bug is present on POWER4 and JS20.
+ */
+#define EXCEPTION_PROLOG_PSERIES_FORCE_64BIT(area, label)               \
+        mfspr   r13,SPRN_SPRG3;         /* get paca address into r13 */ \
+        std     r9,area+EX_R9(r13);     /* save r9 - r12 */             \
+        std     r10,area+EX_R10(r13);                                   \
+        std     r11,area+EX_R11(r13);                                   \
+        std     r12,area+EX_R12(r13);                                   \
+        mfspr   r9,SPRN_SPRG1;                                          \
+        std     r9,area+EX_R13(r13);                                    \
+        mfcr    r9;                                                     \
+        clrrdi  r12,r13,32;             /* get high part of &label */   \
+        mfmsr   r10;                                                    \
+        /* force 64bit mode */                                          \
+        li      r11,5;                  /* MSR_SF_LG|MSR_ISF_LG */      \
+        rldimi  r10,r11,61,0;           /* insert into top 3 bits */    \
+        /* done 64bit mode */                                           \
+        mfspr   r11,SPRN_SRR0;          /* save SRR0 */                 \
+        LOAD_HANDLER(r12,label)                                         \
+        ori     r10,r10,MSR_IR|MSR_DR|MSR_RI;                           \
+        mtspr   SPRN_SRR0,r12;                                          \
+        mfspr   r12,SPRN_SRR1;          /* and SRR1 */                  \
+        mtspr   SPRN_SRR1,r10;                                          \
+        rfid;                                                           \
+        b       .       /* prevent speculative execution */
+
 #define EXCEPTION_PROLOG_PSERIES(area, label)                           \
         mfspr   r13,SPRN_SPRG3;         /* get paca address into r13 */ \
         std     r9,area+EX_R9(r13);     /* save r9 - r12 */             \
@@ -604,14 +635,14 @@ slb_miss_user_pseries:
 system_reset_fwnmi:
         HMT_MEDIUM
         mtspr   SPRN_SPRG1,r13          /* save r13 */
-        EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, system_reset_common)
+        EXCEPTION_PROLOG_PSERIES_FORCE_64BIT(PACA_EXGEN, system_reset_common)
 
         .globl machine_check_fwnmi
       .align 7
 machine_check_fwnmi:
         HMT_MEDIUM
         mtspr   SPRN_SPRG1,r13          /* save r13 */
-        EXCEPTION_PROLOG_PSERIES(PACA_EXMC, machine_check_common)
+        EXCEPTION_PROLOG_PSERIES_FORCE_64BIT(PACA_EXMC, machine_check_common)
 
 #ifdef CONFIG_PPC_ISERIES
 /***  ISeries-LPAR interrupt handlers ***/