Patch "MIPS: Flush wrong invalid FTLB entry for huge page" has been added to the 4.4-stable tree

PATCH [email protected] 1 participant 1 message Apr 10, 2017

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2017-04-10 14:46 UTC #0 lore raw

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

MIPS: Flush wrong invalid FTLB entry for huge page

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:
mips-flush-wrong-invalid-ftlb-entry-for-huge-page.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.

Quoted 1 line

From 0115f6cbf26663c86496bc56eeea293f85b77897 Mon Sep 17 00:00:00 2001

From: Huacai Chen <[email protected]>
Date: Thu, 16 Mar 2017 21:00:27 +0800
Subject: MIPS: Flush wrong invalid FTLB entry for huge page

From: Huacai Chen <[email protected]>

commit 0115f6cbf26663c86496bc56eeea293f85b77897 upstream.

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.

Signed-off-by Rui Wang <[email protected]>

Signed-off-by Huacai Chen <[email protected]>

Cc John Crispin <[email protected]>

Cc Steven J . Hill <[email protected]>

Cc Fuxin Zhang <[email protected]>

Cc Zhangjin Wu <[email protected]>

Cc Huacai Chen <[email protected]>

Cc [email protected]

Patchwork: https://patchwork.linux-mips.org/patch/15754/

Signed-off-by Ralf Baechle <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 arch/mips/mm/tlbex.c |   25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

arch/mips/mm/tlbex.c +21 -4

@@ -757,7 +757,8 @@ static void build_huge_update_entries(u3
 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);

@@ -766,6 +767,22 @@ static void build_huge_handler_tail(u32
 #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);
 }

@@ -2082,7 +2099,7 @@ static void build_r4000_tlb_load_handler
 		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);

@@ -2137,7 +2154,7 @@ static void build_r4000_tlb_store_handle
 	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);

@@ -2193,7 +2210,7 @@ static void build_r4000_tlb_modify_handl
 	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);

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

queue-4.4/mips-flush-wrong-invalid-ftlb-entry-for-huge-page.patch