powerpc/64s: Convert slb_miss_common to use RFI_TO_USER/KERNEL

In the SLB miss handler we may be returning to user or kernel. We need
to add a check early on and save the result in the cr4 register, and
then we bifurcate the return path based on that.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 28 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 5502b0147c4e..ed356194f09c 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -598,6 +598,9 @@ EXC_COMMON_BEGIN(slb_miss_common)
         stw     r9,PACA_EXSLB+EX_CCR(r13)       /* save CR in exc. frame */
         std     r10,PACA_EXSLB+EX_LR(r13)       /* save LR */
 
+        andi.   r9,r11,MSR_PR   // Check for exception from userspace
+        cmpdi   cr4,r9,MSR_PR   // And save the result in CR4 for later
+
         /*
          * Test MSR_RI before calling slb_allocate_realmode, because the
          * MSR in r11 gets clobbered. However we still want to allocate
@@ -624,9 +627,32 @@ END_MMU_FTR_SECTION_IFCLR(MMU_FTR_TYPE_RADIX)
 
         /* All done -- return from exception. */
 
+        bne     cr4,1f          /* returning to kernel */
+
+.machine        push
+.machine        "power4"
+        mtcrf   0x80,r9
+        mtcrf   0x08,r9         /* MSR[PR] indication is in cr4 */
+        mtcrf   0x04,r9         /* MSR[RI] indication is in cr5 */
+        mtcrf   0x02,r9         /* I/D indication is in cr6 */
+        mtcrf   0x01,r9         /* slb_allocate uses cr0 and cr7 */
+.machine        pop
+
+        RESTORE_CTR(r9, PACA_EXSLB)
+        RESTORE_PPR_PACA(PACA_EXSLB, r9)
+        mr      r3,r12
+        ld      r9,PACA_EXSLB+EX_R9(r13)
+        ld      r10,PACA_EXSLB+EX_R10(r13)
+        ld      r11,PACA_EXSLB+EX_R11(r13)
+        ld      r12,PACA_EXSLB+EX_R12(r13)
+        ld      r13,PACA_EXSLB+EX_R13(r13)
+        RFI_TO_USER
+        b       .       /* prevent speculative execution */
+1:
 .machine        push
 .machine        "power4"
         mtcrf   0x80,r9
+        mtcrf   0x08,r9         /* MSR[PR] indication is in cr4 */
         mtcrf   0x04,r9         /* MSR[RI] indication is in cr5 */
         mtcrf   0x02,r9         /* I/D indication is in cr6 */
         mtcrf   0x01,r9         /* slb_allocate uses cr0 and cr7 */
@@ -640,9 +666,10 @@ END_MMU_FTR_SECTION_IFCLR(MMU_FTR_TYPE_RADIX)
         ld      r11,PACA_EXSLB+EX_R11(r13)
         ld      r12,PACA_EXSLB+EX_R12(r13)
         ld      r13,PACA_EXSLB+EX_R13(r13)
-        rfid
+        RFI_TO_KERNEL
         b       .       /* prevent speculative execution */
 
+
 2:      std     r3,PACA_EXSLB+EX_DAR(r13)
         mr      r3,r12
         mfspr   r11,SPRN_SRR0