linux-kernel - [PATCH] x86/mm: fix return value of p[um]dp_set_access

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Message-Id: <20190919082549.3895-1-richardw.yang@linux.intel.com>
Date:   Thu, 19 Sep 2019 16:25:49 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Wei Yang <richardw.yang@...ux.intel.com>
Subject: [PATCH] x86/mm: fix return value of p[um]dp_set_access_flags

Function p[um]dp_set_access_flags is used with update_mmu_cache_p[um]d
and the return value from p[um]dp_set_access_flags indicates whether it
is necessary to do the cache update.

>From current code logic, only when changed && dirty, related page table
entry would be updated. It is not necessary to update cache when the
real page table entry is not changed.

Signed-off-by: Wei Yang <richardw.yang@...ux.intel.com>
---
 arch/x86/mm/pgtable.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 44816ff6411f..ba910f8ab43a 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -509,9 +509,10 @@ int pmdp_set_access_flags(struct vm_area_struct *vma,
 		 * #PF is architecturally guaranteed to do that and in the
 		 * worst-case we'll generate a spurious fault.
 		 */
+		return true;
 	}
 
-	return changed;
+	return false;
 }
 
 int pudp_set_access_flags(struct vm_area_struct *vma, unsigned long address,
@@ -529,9 +530,10 @@ int pudp_set_access_flags(struct vm_area_struct *vma, unsigned long address,
 		 * #PF is architecturally guaranteed to do that and in the
 		 * worst-case we'll generate a spurious fault.
 		 */
+		return true;
 	}
 
-	return changed;
+	return false;
 }
 #endif
 
-- 
2.17.1