From: Lai Jiangshan <laijs@cn.fujitsu.com>
Subject: [PATCH] kvm: reduce couple for ACC_EXEC_MASK
Date: Sat, 17 Apr 2010 17:08:13 +0800
Message-ID: <4BC97A7D.4070502@cn.fujitsu.com>
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To: Avi Kivity <avi@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>, kvm@vger.kernel.org
Return-path: <linux-kernel-owner@vger.kernel.org>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org


The statement "access &= ~(gpte >> PT64_NX_SHIFT);" tries
to clear bit ACC_EXEC_MASK actually. This statement
relies PT64_NX_SHIFT==63&&ACC_EXEC_MASK=1

This patch reduces this couple.


Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 81eab9a..34f4aa2 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -101,11 +101,9 @@ static unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, pt_element_t gpte)
 {
 	unsigned access;
 
-	access = (gpte & (PT_WRITABLE_MASK | PT_USER_MASK)) | ACC_EXEC_MASK;
-#if PTTYPE == 64
-	if (is_nx(vcpu))
-		access &= ~(gpte >> PT64_NX_SHIFT);
-#endif
+	access = (gpte & (PT_WRITABLE_MASK | PT_USER_MASK));
+	if (PTTYPE != 64 || !is_nx(vcpu) || (gpte & PT64_NX_MASK))
+		access |= ACC_EXEC_MASK;
 	return access;
 }