3 files changed, 35 insertions, 3 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 0b7553cbc52..bd74229081c 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -168,7 +168,9 @@ static void __init xen_banner(void)
 {
 	printk(KERN_INFO "Booting paravirtualized kernel on %s\n",
 	       pv_info.name);
-	printk(KERN_INFO "Hypervisor signature: %s\n", xen_start_info->magic);
+	printk(KERN_INFO "Hypervisor signature: %s%s\n",
+	       xen_start_info->magic,
+	       xen_feature(XENFEAT_mmu_pt_update_preserve_ad) ? " (preserve-AD)" : "");
 }
 
 static void xen_cpuid(unsigned int *ax, unsigned int *bx,
@@ -1243,6 +1245,8 @@ asmlinkage void __init xen_start_kernel(void)
 
 	BUG_ON(memcmp(xen_start_info->magic, "xen-3", 5) != 0);
 
+	xen_setup_features();
+
 	/* Install Xen paravirt ops */
 	pv_info = xen_info;
 	pv_init_ops = xen_init_ops;
@@ -1252,14 +1256,17 @@ asmlinkage void __init xen_start_kernel(void)
 	pv_apic_ops = xen_apic_ops;
 	pv_mmu_ops = xen_mmu_ops;
 
+	if (xen_feature(XENFEAT_mmu_pt_update_preserve_ad)) {
+		pv_mmu_ops.ptep_modify_prot_start = xen_ptep_modify_prot_start;
+		pv_mmu_ops.ptep_modify_prot_commit = xen_ptep_modify_prot_commit;
+	}
+
 	machine_ops = xen_machine_ops;
 
 #ifdef CONFIG_SMP
 	smp_ops = xen_smp_ops;
 #endif
 
-	xen_setup_features();
-
 	/* Get mfn list */
 	if (!xen_feature(XENFEAT_auto_translated_physmap))
 		xen_build_dynamic_phys_to_machine();
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 8132aa8c5d4..846dad7d54a 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -323,6 +323,27 @@ out:
 		preempt_enable();
 }
 
+pte_t xen_ptep_modify_prot_start(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
+{
+	/* Just return the pte as-is.  We preserve the bits on commit */
+	return *ptep;
+}
+
+void xen_ptep_modify_prot_commit(struct mm_struct *mm, unsigned long addr,
+				 pte_t *ptep, pte_t pte)
+{
+	struct multicall_space mcs;
+	struct mmu_update *u;
+
+	mcs = xen_mc_entry(sizeof(*u));
+	u = mcs.args;
+	u->ptr = virt_to_machine(ptep).maddr | MMU_PT_UPDATE_PRESERVE_AD;
+	u->val = pte_val_ma(pte);
+	MULTI_mmu_update(mcs.mc, u, 1, NULL, DOMID_SELF);
+
+	xen_mc_issue(PARAVIRT_LAZY_MMU);
+}
+
 /* Assume pteval_t is equivalent to all the other *val_t types. */
 static pteval_t pte_mfn_to_pfn(pteval_t val)
 {
diff --git a/arch/x86/xen/mmu.h b/arch/x86/xen/mmu.h
index e3dd09e25c6..297bf9f5b8b 100644
--- a/arch/x86/xen/mmu.h
+++ b/arch/x86/xen/mmu.h
@@ -52,4 +52,8 @@ void xen_set_pud_hyper(pud_t *ptr, pud_t val);
 void xen_pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep);
 void xen_pmd_clear(pmd_t *pmdp);
 
+pte_t xen_ptep_modify_prot_start(struct mm_struct *mm, unsigned long addr, pte_t *ptep);
+void  xen_ptep_modify_prot_commit(struct mm_struct *mm, unsigned long addr,
+				  pte_t *ptep, pte_t pte);
+
 #endif	/* _XEN_MMU_H */