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[PATCH RESEND 3/4] MIPS: Flush wrong invalid FTLB entry for huge page

To: Ralf Baechle <ralf@linux-mips.org>
Subject: [PATCH RESEND 3/4] MIPS: Flush wrong invalid FTLB entry for huge page
From: Huacai Chen <chenhc@lemote.com>
Date: Sat, 21 Jan 2017 14:34:01 +0800
Cc: John Crispin <john@phrozen.org>, "Steven J . Hill" <Steven.Hill@imgtec.com>, linux-mips@linux-mips.org, Fuxin Zhang <zhangfx@lemote.com>, Zhangjin Wu <wuzhangjin@gmail.com>, Huacai Chen <chenhc@lemote.com>, stable@vger.kernel.org, Rui Wang <wangr@lemote.com>
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On VTLB+FTLB platforms (such as Loongson-3A R2), FTLB's pagesize is
usually configured the same as PAGE_SIZE. In such a case, Huge page
entry is not suitable to write in FTLB.

Unfortunately, when a huge page is created, its page table entries
haven't created immediately. Then the TLB refill handler will fetch an
invalid page table entry which has no "HUGE" bit, and this entry may be
written to FTLB. Since it is invalid, TLB load/store handler will then
use tlbwi to write the valid entry at the same place. However, the
valid entry is a huge page entry which isn't suitable for FTLB.

Our solution is to modify build_huge_handler_tail. Flush the invalid
old entry (whether it is in FTLB or VTLB, this is in order to reduce
branches) and use tlbwr to write the valid new entry.

Cc: stable@vger.kernel.org
Signed-off-by: Rui Wang <wangr@lemote.com>
Signed-off-by: Huacai Chen <chenhc@lemote.com>
---
 arch/mips/mm/tlbex.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index 87eed65..aabc413 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -762,7 +762,8 @@ static void build_huge_update_entries(u32 **p, unsigned int 
pte,
 static void build_huge_handler_tail(u32 **p, struct uasm_reloc **r,
                                    struct uasm_label **l,
                                    unsigned int pte,
-                                   unsigned int ptr)
+                                   unsigned int ptr,
+                                   unsigned int flush)
 {
 #ifdef CONFIG_SMP
        UASM_i_SC(p, pte, 0, ptr);
@@ -771,6 +772,22 @@ static void build_huge_handler_tail(u32 **p, struct 
uasm_reloc **r,
 #else
        UASM_i_SW(p, pte, 0, ptr);
 #endif
+       if (cpu_has_ftlb && flush) {
+               BUG_ON(!cpu_has_tlbinv);
+
+               UASM_i_MFC0(p, ptr, C0_ENTRYHI);
+               uasm_i_ori(p, ptr, ptr, MIPS_ENTRYHI_EHINV);
+               UASM_i_MTC0(p, ptr, C0_ENTRYHI);
+               build_tlb_write_entry(p, l, r, tlb_indexed);
+
+               uasm_i_xori(p, ptr, ptr, MIPS_ENTRYHI_EHINV);
+               UASM_i_MTC0(p, ptr, C0_ENTRYHI);
+               build_huge_update_entries(p, pte, ptr);
+               build_huge_tlb_write_entry(p, l, r, pte, tlb_random, 0);
+
+               return;
+       }
+
        build_huge_update_entries(p, pte, ptr);
        build_huge_tlb_write_entry(p, l, r, pte, tlb_indexed, 0);
 }
@@ -2197,7 +2214,7 @@ static void build_r4000_tlb_load_handler(void)
                uasm_l_tlbl_goaround2(&l, p);
        }
        uasm_i_ori(&p, wr.r1, wr.r1, (_PAGE_ACCESSED | _PAGE_VALID));
-       build_huge_handler_tail(&p, &r, &l, wr.r1, wr.r2);
+       build_huge_handler_tail(&p, &r, &l, wr.r1, wr.r2, 1);
 #endif
 
        uasm_l_nopage_tlbl(&l, p);
@@ -2252,7 +2269,7 @@ static void build_r4000_tlb_store_handler(void)
        build_tlb_probe_entry(&p);
        uasm_i_ori(&p, wr.r1, wr.r1,
                   _PAGE_ACCESSED | _PAGE_MODIFIED | _PAGE_VALID | _PAGE_DIRTY);
-       build_huge_handler_tail(&p, &r, &l, wr.r1, wr.r2);
+       build_huge_handler_tail(&p, &r, &l, wr.r1, wr.r2, 1);
 #endif
 
        uasm_l_nopage_tlbs(&l, p);
@@ -2308,7 +2325,7 @@ static void build_r4000_tlb_modify_handler(void)
        build_tlb_probe_entry(&p);
        uasm_i_ori(&p, wr.r1, wr.r1,
                   _PAGE_ACCESSED | _PAGE_MODIFIED | _PAGE_VALID | _PAGE_DIRTY);
-       build_huge_handler_tail(&p, &r, &l, wr.r1, wr.r2);
+       build_huge_handler_tail(&p, &r, &l, wr.r1, wr.r2, 0);
 #endif
 
        uasm_l_nopage_tlbm(&l, p);
-- 
2.7.0




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