linux-kernel - [PATCH] MIPS: update tlb even if pte entry has no change

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Date:   Thu, 14 May 2020 10:17:57 +0800
From:   Bibo Mao <maobibo@...ngson.cn>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Paul Burton <paulburton@...nel.org>,
        Dmitry Korotin <dkorotin@...ecomp.com>,
        Philippe Mathieu-Daudé <f4bug@...at.org>,
        Stafford Horne <shorne@...il.com>,
        Steven Price <steven.price@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Mike Rapoport <rppt@...ux.ibm.com>
Cc:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        bibo mao <maobibo@...ngson.cn>
Subject: [PATCH] MIPS: update tlb even if pte entry has no change

From: bibo mao <maobibo@...ngson.cn>

If there are two threads reading the same memory and tlb miss happens,
one thread fills pte entry, the other reads new pte value during page fault
handling. PTE value may be updated before page faul, so the process need
need update tlb still.

Also this patch define flush_tlb_fix_spurious_fault as empty, since it not
necessary to flush the page for all CPUs

Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
---
 arch/mips/include/asm/pgtable.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
index aab0ec1..d0a4940 100644
--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -635,6 +635,26 @@ static inline pmd_t pmd_mknotpresent(pmd_t pmd)
 	return pmd;
 }
 
+#define flush_tlb_fix_spurious_fault(vma, address) do { } while (0)
+
+#define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
+int ptep_set_access_flags(struct vm_area_struct *vma,
+			unsigned long address, pte_t *ptep,
+			pte_t entry, int dirty)
+{
+	int changed = !pte_same(*ptep, entry);
+
+	if (changed)
+		set_pte_at(vma->vm_mm, address, ptep, entry);
+	else
+		/* update tlb with latest pte entry still, tlb entry is old
+		 * since there is page fault
+		 */
+		update_mmu_cache(vma, address, ptep);
+
+	return changed;
+}
+
 /*
  * The generic version pmdp_huge_get_and_clear uses a version of pmd_clear() with a
  * different prototype.
-- 
1.8.3.1