Patch "MIPS: Check TLB before handle_ri_rdhwr() for Loongson-3" has been added to the 4.9-stable tree

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

MIPS: Check TLB before handle_ri_rdhwr() for Loongson-3

to the 4.9-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:
mips-check-tlb-before-handle_ri_rdhwr-for-loongson-3.patch
and it can be found in the queue-4.9 subdirectory.

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

From: Huacai Chen <[email protected]>
Date: Thu, 16 Mar 2017 21:00:26 +0800
Subject: MIPS: Check TLB before handle_ri_rdhwr() for Loongson-3

From: Huacai Chen <[email protected]>

commit 5a34133167dce36666ea054e30a561b7f4413b7f upstream.

Loongson-3's micro TLB (ITLB) is not strictly a subset of JTLB. That
means: when a JTLB entry is replaced by hardware, there may be an old valid entry exists in ITLB. So, a TLB miss exception may occur while handle_ri_rdhwr() is running because it try to access EPC's content. However, handle_ri_rdhwr() doesn't clear EXL, which makes a TLB Refill exception be treated as a TLB Invalid exception and tlbp may fail. In this case, if FTLB (which is usually set-associative instead of set- associative) is enabled, a tlbp failure will cause an invalid tlbwi, which will hang the whole system.

This patch rename handle_ri_rdhwr_vivt to handle_ri_rdhwr_tlbp and use it for Loongson-3. It try to solve the same problem described as below, but more straightforwards.

https://patchwork.linux-mips.org/patch/12591/

I think Loongson-2 has the same problem, but it has no FTLB, so we just keep it as is.

Patchwork: https://patchwork.linux-mips.org/patch/15753/

---
 arch/mips/kernel/genex.S |    4 ++--
 arch/mips/kernel/traps.c |   17 +++++++++++++----
 2 files changed, 15 insertions(+), 6 deletions(-)

@@ -448,7 +448,7 @@ NESTED(nmi_handler, PT_SIZE, sp)
 	BUILD_HANDLER reserved reserved sti verbose	/* others */
 
 	.align	5
-	LEAF(handle_ri_rdhwr_vivt)
+	LEAF(handle_ri_rdhwr_tlbp)
 	.set	push
 	.set	noat
 	.set	noreorder

@@ -467,7 +467,7 @@ NESTED(nmi_handler, PT_SIZE, sp)
 	.set	pop
 	bltz	k1, handle_ri	/* slow path */
 	/* fall thru */
-	END(handle_ri_rdhwr_vivt)
+	END(handle_ri_rdhwr_tlbp)
 
 	LEAF(handle_ri_rdhwr)
 	.set	push

@@ -81,7 +81,7 @@ extern asmlinkage void handle_dbe(void);
 extern asmlinkage void handle_sys(void);
 extern asmlinkage void handle_bp(void);
 extern asmlinkage void handle_ri(void);
-extern asmlinkage void handle_ri_rdhwr_vivt(void);
+extern asmlinkage void handle_ri_rdhwr_tlbp(void);
 extern asmlinkage void handle_ri_rdhwr(void);
 extern asmlinkage void handle_cpu(void);
 extern asmlinkage void handle_ov(void);

@@ -2352,9 +2352,18 @@ void __init trap_init(void)
 
 	set_except_vector(EXCCODE_SYS, handle_sys);
 	set_except_vector(EXCCODE_BP, handle_bp);
-	set_except_vector(EXCCODE_RI, rdhwr_noopt ? handle_ri :
-			  (cpu_has_vtag_icache ?
-			   handle_ri_rdhwr_vivt : handle_ri_rdhwr));
+
+	if (rdhwr_noopt)
+		set_except_vector(EXCCODE_RI, handle_ri);
+	else {
+		if (cpu_has_vtag_icache)
+			set_except_vector(EXCCODE_RI, handle_ri_rdhwr_tlbp);
+		else if (current_cpu_type() == CPU_LOONGSON3)
+			set_except_vector(EXCCODE_RI, handle_ri_rdhwr_tlbp);
+		else
+			set_except_vector(EXCCODE_RI, handle_ri_rdhwr);
+	}
+
 	set_except_vector(EXCCODE_CPU, handle_cpu);
 	set_except_vector(EXCCODE_OV, handle_ov);
 	set_except_vector(EXCCODE_TR, handle_tr);

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

queue-4.9/mips-flush-wrong-invalid-ftlb-entry-for-huge-page.patch queue-4.9/mips-check-tlb-before-handle_ri_rdhwr-for-loongson-3.patch queue-4.9/mips-c-r4k-fix-loongson-3-s-vcache-scache-waysize-calculation.patch queue-4.9/mips-add-mips_cpu_ftlb-for-loongson-3a-r2.patch