KVM: x86: MMU: always set accessed bit in shadow PTEs

Commit 7a1638ce42 ("nEPT: Redefine EPT-specific link_shadow_page()",
2013-08-05) says:

    Since nEPT doesn't support A/D bit, we should not set those bit
    when building the shadow page table.

but this is not necessary.  Even though nEPT doesn't support A/D
bits, and hence the vmcs12 EPT pointer will never enable them,
we always use them for shadow page tables if available (see
construct_eptp in vmx.c).  So we can set the A/D bits freely
in the shadow page table.

This patch hence basically reverts commit 7a1638ce42.

Cc: Yang Zhang <yang.z.zhang@Intel.com>
Cc: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/paging_tmpl.h

@@ -598,7 +598,7 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
 			goto out_gpte_changed;
 
 		if (sp)
-			link_shadow_page(it.sptep, sp, PT_GUEST_ACCESSED_MASK);
+			link_shadow_page(it.sptep, sp);
 	}
 
 	for (;
@@ -618,7 +618,7 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
 
 		sp = kvm_mmu_get_page(vcpu, direct_gfn, addr, it.level-1,
 				      true, direct_access, it.sptep);
-		link_shadow_page(it.sptep, sp, PT_GUEST_ACCESSED_MASK);
+		link_shadow_page(it.sptep, sp);
 	}
 
 	clear_sp_write_flooding_count(it.sptep);