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Subject[PATCH 4.10 057/110] MIPS: Check TLB before handle_ri_rdhwr() for Loongson-3
Date
4.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Huacai Chen <chenhc@lemote.com>

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.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Cc: Rui Wang <wangr@lemote.com>
Cc: John Crispin <john@phrozen.org>
Cc: Steven J . Hill <Steven.Hill@caviumnetworks.com>
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Cc: Huacai Chen <chenhc@lemote.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15753/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/arch/mips/kernel/genex.S
+++ b/arch/mips/kernel/genex.S
@@ -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
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -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);

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