Patch "powerpc/64s: Convert slb_miss_common to use RFI_TO_USER/KERNEL" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

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

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
powerpc-64s-convert-slb_miss_common-to-use-rfi_to_user-kernel.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Nicholas Piggin <[email protected]>
Date: Wed, 10 Jan 2018 03:07:15 +1100
Subject: powerpc/64s: Convert slb_miss_common to use RFI_TO_USER/KERNEL

From: Nicholas Piggin <[email protected]>

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.

---
 arch/powerpc/kernel/exceptions-64s.S |   22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

@@ -1503,6 +1503,8 @@ 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"

@@ -1516,7 +1518,23 @@ 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

@@ -1525,7 +1543,7 @@ slb_miss_realmode:
 	mtspr	SPRN_SRR0,r10
 	ld	r10,PACAKMSR(r13)
 	mtspr	SPRN_SRR1,r10
-	rfid
+	RFI_TO_KERNEL
 	b	.
 
 unrecov_slb:

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/powerpc-64s-simple-rfi-macro-conversions.patch queue-4.4/powerpc-64-add-macros-for-annotating-the-destination-of-rfid-hrfid.patch queue-4.4/powerpc-64s-allow-control-of-rfi-flush-via-debugfs.patch queue-4.4/powerpc-64s-convert-slb_miss_common-to-use-rfi_to_user-kernel.patch queue-4.4/powerpc-64-convert-the-syscall-exit-path-to-use-rfi_to_user-kernel.patch queue-4.4/powerpc-64s-add-support-for-rfi-flush-of-l1-d-cache.patch queue-4.4/powerpc-64-convert-fast_exception_return-to-use-rfi_to_user-kernel.patch