linux-kernel - [PATCH 1/2] Revert "MIPS: Remove race window in page fault handling"

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Date:	Thu, 26 Feb 2015 14:16:02 +0100
From:	Lars Persson <lars.persson@...s.com>
To:	linux-mips@...ux-mips.org, ralf@...ux-mips.org,
	paul.burton@...tec.com
Cc:	linux-kernel@...r.kernel.org, Lars Persson <larper@...s.com>
Subject: [PATCH 1/2] Revert "MIPS: Remove race window in page fault handling"

Revert commit 2a4a8b1e5d9d ("MIPS: Remove race window in page fault
handling") because it increased the number of flushed dcache pages and
became a performance problem for some workloads.

Signed-off-by: Lars Persson <larper@...s.com>
---
 arch/mips/include/asm/pgtable.h |   10 ++++++----
 arch/mips/mm/cache.c            |   27 ++++++++-------------------
 2 files changed, 14 insertions(+), 23 deletions(-)

diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
index bef782c..bd6d1cf 100644
--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -127,12 +127,9 @@ do {									\
 	}								\
 } while(0)
 
-
-extern void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
-	pte_t pteval);
-
 #if defined(CONFIG_PHYS_ADDR_T_64BIT) && defined(CONFIG_CPU_MIPS32)
 
+
 #define pte_none(pte)		(!(((pte).pte_low | (pte).pte_high) & ~_PAGE_GLOBAL))
 #define pte_present(pte)	((pte).pte_low & _PAGE_PRESENT)
 
@@ -154,6 +151,7 @@ static inline void set_pte(pte_t *ptep, pte_t pte)
 		}
 	}
 }
+#define set_pte_at(mm, addr, ptep, pteval) set_pte(ptep, pteval)
 
 static inline void pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
 {
@@ -192,6 +190,7 @@ static inline void set_pte(pte_t *ptep, pte_t pteval)
 	}
 #endif
 }
+#define set_pte_at(mm, addr, ptep, pteval) set_pte(ptep, pteval)
 
 static inline void pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
 {
@@ -407,12 +406,15 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 
 extern void __update_tlb(struct vm_area_struct *vma, unsigned long address,
 	pte_t pte);
+extern void __update_cache(struct vm_area_struct *vma, unsigned long address,
+	pte_t pte);
 
 static inline void update_mmu_cache(struct vm_area_struct *vma,
 	unsigned long address, pte_t *ptep)
 {
 	pte_t pte = *ptep;
 	__update_tlb(vma, address, pte);
+	__update_cache(vma, address, pte);
 }
 
 static inline void update_mmu_cache_pmd(struct vm_area_struct *vma,
diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
index 7e3ea77..f7b91d3 100644
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -119,36 +119,25 @@ void __flush_anon_page(struct page *page, unsigned long vmaddr)
 
 EXPORT_SYMBOL(__flush_anon_page);
 
-static void mips_flush_dcache_from_pte(pte_t pteval, unsigned long address)
+void __update_cache(struct vm_area_struct *vma, unsigned long address,
+	pte_t pte)
 {
 	struct page *page;
-	unsigned long pfn = pte_pfn(pteval);
+	unsigned long pfn, addr;
+	int exec = (vma->vm_flags & VM_EXEC) && !cpu_has_ic_fills_f_dc;
 
+	pfn = pte_pfn(pte);
 	if (unlikely(!pfn_valid(pfn)))
 		return;
-
 	page = pfn_to_page(pfn);
 	if (page_mapping(page) && Page_dcache_dirty(page)) {
-		unsigned long page_addr = (unsigned long) page_address(page);
-
-		if (!cpu_has_ic_fills_f_dc ||
-		    pages_do_alias(page_addr, address & PAGE_MASK))
-			flush_data_cache_page(page_addr);
+		addr = (unsigned long) page_address(page);
+		if (exec || pages_do_alias(addr, address & PAGE_MASK))
+			flush_data_cache_page(addr);
 		ClearPageDcacheDirty(page);
 	}
 }
 
-void set_pte_at(struct mm_struct *mm, unsigned long addr,
-        pte_t *ptep, pte_t pteval)
-{
-        if (cpu_has_dc_aliases || !cpu_has_ic_fills_f_dc) {
-                if (pte_present(pteval))
-                        mips_flush_dcache_from_pte(pteval, addr);
-        }
-
-        set_pte(ptep, pteval);
-}
-
 unsigned long _page_cachable_default;
 EXPORT_SYMBOL(_page_cachable_default);
 
-- 
1.7.10.4

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