Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Message-Id: <20181226133351.828074959@intel.com>
User-Agent: quilt/0.65
Date:   Wed, 26 Dec 2018 21:14:59 +0800
From:   Fengguang Wu <fengguang.wu@intel.com>
To:     Andrew Morton <akpm@linux-foundation.org>
cc:     Linux Memory Management List <linux-mm@kvack.org>,
        Jingqi Liu <jingqi.liu@intel.com>,
        Fengguang Wu <fengguang.wu@intel.com>
cc:     kvm@vger.kernel.org
Cc:     LKML <linux-kernel@vger.kernel.org>
cc:     Fan Du <fan.du@intel.com>
cc:     Yao Yuan <yuan.yao@intel.com>
cc:     Peng Dong <dongx.peng@intel.com>
cc:     Huang Ying <ying.huang@intel.com>
cc:     Dong Eddie <eddie.dong@intel.com>
cc:     Dave Hansen <dave.hansen@intel.com>
cc:     Zhang Yi <yi.z.zhang@linux.intel.com>
cc:     Dan Williams <dan.j.williams@intel.com>
Subject: [RFC][PATCH v2 13/21] x86/pgtable: dont check PMD accessed bit
References: <20181226131446.330864849@intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Disposition: inline; filename=0006-pgtable-don-t-check-the-page-accessed-bit.patch
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Jingqi Liu <jingqi.liu@intel.com>

ept-idle will clear PMD accessed bit to speedup PTE scan -- if the bit
remains unset in the next scan, all the 512 PTEs can be skipped.

So don't complain on !_PAGE_ACCESSED in pmd_bad().

Note that clearing PMD accessed bit has its own cost, the optimization
may only be worthwhile for
- large idle area
- sparsely populated area

Signed-off-by: Jingqi Liu <jingqi.liu@intel.com>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
---
 arch/x86/include/asm/pgtable.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- linux.orig/arch/x86/include/asm/pgtable.h	2018-12-23 19:50:50.917902600 +0800
+++ linux/arch/x86/include/asm/pgtable.h	2018-12-23 19:50:50.913902605 +0800
@@ -821,7 +821,8 @@ static inline pte_t *pte_offset_kernel(p
 
 static inline int pmd_bad(pmd_t pmd)
 {
-	return (pmd_flags(pmd) & ~_PAGE_USER) != _KERNPG_TABLE;
+	return (pmd_flags(pmd) & ~(_PAGE_USER | _PAGE_ACCESSED)) !=
+					(_KERNPG_TABLE & ~_PAGE_ACCESSED);
 }
 
 static inline unsigned long pages_to_mb(unsigned long npg)