linux-kernel - [PATCH] x86: make mm/gup.c more virtualization friendly

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Message-Id: <48D142E1.76E4.0078.0@novell.com>
Date:	Wed, 17 Sep 2008 16:48:17 +0100
From:	"Jan Beulich" <jbeulich@...ell.com>
To:	<mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc:	"Nick Piggin" <npiggin@...e.de>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86: make mm/gup.c more virtualization friendly

Since pte_flags() is much cheaper than pte_val() in some virtualized
environments (namely, Xen), use the former whereever possible.

Signed-off-by: Jan Beulich <jbeulich@...ell.com>
Cc: Nick Piggin <npiggin@...e.de>

---
 arch/x86/mm/gup.c         |   10 +++++-----
 include/asm-x86/pgtable.h |    2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

--- linux-2.6.27-rc6/arch/x86/mm/gup.c	2008-08-21 14:37:29.000000000 +0200
+++ 2.6.27-rc6-x86-gup-virt/arch/x86/mm/gup.c	2008-09-02 13:33:42.000000000 +0200
@@ -82,7 +82,7 @@ static noinline int gup_pte_range(pmd_t 
 		pte_t pte = gup_get_pte(ptep);
 		struct page *page;
 
-		if ((pte_val(pte) & (mask | _PAGE_SPECIAL)) != mask) {
+		if ((pte_flags(pte) & (mask | _PAGE_SPECIAL)) != mask) {
 			pte_unmap(ptep);
 			return 0;
 		}
@@ -116,10 +116,10 @@ static noinline int gup_huge_pmd(pmd_t p
 	mask = _PAGE_PRESENT|_PAGE_USER;
 	if (write)
 		mask |= _PAGE_RW;
-	if ((pte_val(pte) & mask) != mask)
+	if ((pte_flags(pte) & mask) != mask)
 		return 0;
 	/* hugepages are never "special" */
-	VM_BUG_ON(pte_val(pte) & _PAGE_SPECIAL);
+	VM_BUG_ON(pte_flags(pte) & _PAGE_SPECIAL);
 	VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
 
 	refs = 0;
@@ -173,10 +173,10 @@ static noinline int gup_huge_pud(pud_t p
 	mask = _PAGE_PRESENT|_PAGE_USER;
 	if (write)
 		mask |= _PAGE_RW;
-	if ((pte_val(pte) & mask) != mask)
+	if ((pte_flags(pte) & mask) != mask)
 		return 0;
 	/* hugepages are never "special" */
-	VM_BUG_ON(pte_val(pte) & _PAGE_SPECIAL);
+	VM_BUG_ON(pte_flags(pte) & _PAGE_SPECIAL);
 	VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
 
 	refs = 0;
--- linux-2.6.27-rc6/include/asm-x86/pgtable.h	2008-08-21 14:37:34.000000000 +0200
+++ 2.6.27-rc6-x86-gup-virt/include/asm-x86/pgtable.h	2008-09-02 13:31:50.000000000 +0200
@@ -183,7 +183,7 @@ static inline int pte_exec(pte_t pte)
 
 static inline int pte_special(pte_t pte)
 {
-	return pte_val(pte) & _PAGE_SPECIAL;
+	return pte_flags(pte) & _PAGE_SPECIAL;
 }
 
 static inline int pmd_large(pmd_t pte)



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