[PATCH 4/6] MIPS: tlbex: Fix bugs in tlbchange handler

[Huacai Chen <chenhc@xxxxxxxxxx>]

If a tlb miss triggered when EXL=1, tlb refill exception is treated as
tlb invalid exception, so tlbp may fails. In this situation, CP0_Index
register doesn't contain a valid value. This may not be a problem for
VTLB since it is fully-associative. However, FTLB is set-associative so
not every tlb entry is valid for a specific address. Thus, we should
use tlbwr instead of tlbwi when tlbp fails.

There is a similar case for huge page, so build_huge_tlb_write_entry()
is also modified. If wmode != tlb_random, that means the caller is tlb
invalid handler, we should select tlbr/tlbi depend on the tlbp result.

Signed-off-by: Huacai Chen <chenhc@xxxxxxxxxx>
---
 arch/mips/mm/tlbex.c | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index d0975cd..da68ffb 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -173,7 +173,10 @@ enum label_id {
 	label_large_segbits_fault,
 #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
 	label_tlb_huge_update,
+	label_tail_huge_miss,
+	label_tail_huge_done,
 #endif
+	label_tail_miss,
 };
 
 UASM_L_LA(_second_part)
@@ -192,7 +195,10 @@ UASM_L_LA(_r3000_write_probe_fail)
 UASM_L_LA(_large_segbits_fault)
 #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
 UASM_L_LA(_tlb_huge_update)
+UASM_L_LA(_tail_huge_miss)
+UASM_L_LA(_tail_huge_done)
 #endif
+UASM_L_LA(_tail_miss)
 
 static int hazard_instance;
 
@@ -706,8 +712,24 @@ static void build_huge_tlb_write_entry(u32 **p, struct uasm_label **l,
 	uasm_i_ori(p, tmp, tmp, PM_HUGE_MASK & 0xffff);
 	uasm_i_mtc0(p, tmp, C0_PAGEMASK);
 
-	build_tlb_write_entry(p, l, r, wmode);
+	if (wmode == tlb_random) { /* Caller is TLB Refill Handler */
+		build_tlb_write_entry(p, l, r, wmode);
+		build_restore_pagemask(p, r, tmp, label_leave, restore_scratch);
+		return;
+	}
+
+	/* Caller is TLB Load/Store/Modify Handler */
+	uasm_i_mfc0(p, tmp, C0_INDEX);
+	uasm_il_bltz(p, r, tmp, label_tail_huge_miss);
+	uasm_i_nop(p);
+	build_tlb_write_entry(p, l, r, tlb_indexed);
+	uasm_il_b(p, r, label_tail_huge_done);
+	uasm_i_nop(p);
+
+	uasm_l_tail_huge_miss(l, *p);
+	build_tlb_write_entry(p, l, r, tlb_random);
 
+	uasm_l_tail_huge_done(l, *p);
 	build_restore_pagemask(p, r, tmp, label_leave, restore_scratch);
 }
 
@@ -2026,7 +2048,14 @@ build_r4000_tlbchange_handler_tail(u32 **p, struct uasm_label **l,
 	uasm_i_ori(p, ptr, ptr, sizeof(pte_t));
 	uasm_i_xori(p, ptr, ptr, sizeof(pte_t));
 	build_update_entries(p, tmp, ptr);
+	uasm_i_mfc0(p, ptr, C0_INDEX);
+	uasm_il_bltz(p, r, ptr, label_tail_miss);
+	uasm_i_nop(p);
 	build_tlb_write_entry(p, l, r, tlb_indexed);
+	uasm_il_b(p, r, label_leave);
+	uasm_i_nop(p);
+	uasm_l_tail_miss(l, *p);
+	build_tlb_write_entry(p, l, r, tlb_random);
 	uasm_l_leave(l, *p);
 	build_restore_work_registers(p);
 	uasm_i_eret(p); /* return from trap */
-- 
2.4.6