[PATCH v4.1 backport 06/15] powerpc/64s: Convert slb_miss_common to use RFI_TO_USER/KERNEL

[Michael Ellerman]

From: Nicholas Piggin <npiggin at gmail.com>

commit c7305645eb0c1621351cfc104038831ae87c0053 upstream.

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 at gmail.com>
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
[mpe: Backport to 4.4 based on patch from Balbir]
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 arch/powerpc/kernel/exceptions-64s.S | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 591efc03f80d..c7dfd67c14da 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -1511,6 +1511,8 @@ slb_miss_realmode:
 
 	andi.	r10,r12,MSR_RI	/* check for unrecoverable exception */
 	beq-	2f
+	andi.	r10,r12,MSR_PR	/* check for user mode (PR != 0) */
+	bne	1f
 
 .machine	push
 .machine	"power4"
@@ -1524,7 +1526,23 @@ slb_miss_realmode:
 	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 */
+
+1:
+.machine	push
+.machine	"power4"
+	mtcrf	0x80,r9
+	mtcrf	0x01,r9		/* slb_allocate uses cr0 and cr7 */
+.machine	pop
+
+	RESTORE_PPR_PACA(PACA_EXSLB, r9)
+	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 */
 
 2:	mfspr	r11,SPRN_SRR0
@@ -1533,7 +1551,7 @@ slb_miss_realmode:
 	mtspr	SPRN_SRR0,r10
 	ld	r10,PACAKMSR(r13)
 	mtspr	SPRN_SRR1,r10
-	rfid
+	RFI_TO_KERNEL
 	b	.
 
 unrecov_slb:
-- 
2.14.1