qubes-linux-kernel/patches.xen/xen-x86-pmd-handling

From: jbeulich@novell.com
Subject: consolidate pmd/pud/pgd entry handling
Patch-mainline: obsolete

--- head-2010-04-15.orig/arch/x86/include/mach-xen/asm/hypervisor.h	2010-03-25 14:39:15.000000000 +0100
+++ head-2010-04-15/arch/x86/include/mach-xen/asm/hypervisor.h	2010-03-25 14:41:00.000000000 +0100
@@ -97,10 +97,12 @@ void xen_invlpg(unsigned long ptr);
 void xen_l1_entry_update(pte_t *ptr, pte_t val);
 void xen_l2_entry_update(pmd_t *ptr, pmd_t val);
 void xen_l3_entry_update(pud_t *ptr, pud_t val); /* x86_64/PAE */
-void xen_l4_entry_update(pgd_t *ptr, pgd_t val); /* x86_64 only */
+void xen_l4_entry_update(pgd_t *ptr, int user, pgd_t val); /* x86_64 only */
 void xen_pgd_pin(unsigned long ptr);
 void xen_pgd_unpin(unsigned long ptr);
 
+void xen_init_pgd_pin(void);
+
 void xen_set_ldt(const void *ptr, unsigned int ents);
 
 #ifdef CONFIG_SMP
@@ -333,6 +335,18 @@ MULTI_update_va_mapping(
 }
 
 static inline void
+MULTI_mmu_update(multicall_entry_t *mcl, mmu_update_t *req,
+		 unsigned int count, unsigned int *success_count,
+		 domid_t domid)
+{
+    mcl->op = __HYPERVISOR_mmu_update;
+    mcl->args[0] = (unsigned long)req;
+    mcl->args[1] = count;
+    mcl->args[2] = (unsigned long)success_count;
+    mcl->args[3] = domid;
+}
+
+static inline void
 MULTI_grant_table_op(multicall_entry_t *mcl, unsigned int cmd,
 		     void *uop, unsigned int count)
 {
--- head-2010-04-15.orig/arch/x86/include/mach-xen/asm/pgalloc.h	2010-03-25 16:41:03.000000000 +0100
+++ head-2010-04-15/arch/x86/include/mach-xen/asm/pgalloc.h	2010-03-25 14:41:00.000000000 +0100
@@ -75,20 +75,16 @@ static inline void pmd_populate(struct m
 				struct page *pte)
 {
 	unsigned long pfn = page_to_pfn(pte);
+	pmd_t ent = __pmd(((pmdval_t)pfn << PAGE_SHIFT) | _PAGE_TABLE);
 
 	paravirt_alloc_pte(mm, pfn);
-	if (PagePinned(virt_to_page(mm->pgd))) {
-		if (!PageHighMem(pte))
-			BUG_ON(HYPERVISOR_update_va_mapping(
-			  (unsigned long)__va(pfn << PAGE_SHIFT),
-			  pfn_pte(pfn, PAGE_KERNEL_RO), 0));
-#ifndef CONFIG_X86_64
-		else if (!TestSetPagePinned(pte))
-			kmap_flush_unused();
+	if (PagePinned(virt_to_page(pmd))) {
+#ifndef CONFIG_HIGHPTE
+		BUG_ON(PageHighMem(pte));
 #endif
-		set_pmd(pmd, __pmd(((pmdval_t)pfn << PAGE_SHIFT) | _PAGE_TABLE));
+		set_pmd(pmd, ent);
 	} else
-		*pmd = __pmd(((pmdval_t)pfn << PAGE_SHIFT) | _PAGE_TABLE);
+		*pmd = ent;
 }
 
 #define pmd_pgtable(pmd) pmd_page(pmd)
@@ -116,39 +112,28 @@ extern void pud_populate(struct mm_struc
 #else	/* !CONFIG_X86_PAE */
 static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
 {
+	pud_t ent = __pud(_PAGE_TABLE | __pa(pmd));
+
 	paravirt_alloc_pmd(mm, __pa(pmd) >> PAGE_SHIFT);
-	if (unlikely(PagePinned(virt_to_page((mm)->pgd)))) {
-		BUG_ON(HYPERVISOR_update_va_mapping(
-			       (unsigned long)pmd,
-			       pfn_pte(virt_to_phys(pmd)>>PAGE_SHIFT,
-				       PAGE_KERNEL_RO), 0));
-		set_pud(pud, __pud(_PAGE_TABLE | __pa(pmd)));
-	} else
-		*pud =  __pud(_PAGE_TABLE | __pa(pmd));
+	if (PagePinned(virt_to_page(pud)))
+		set_pud(pud, ent);
+	else
+		*pud = ent;
 }
 #endif	/* CONFIG_X86_PAE */
 
 #if PAGETABLE_LEVELS > 3
 #define __user_pgd(pgd) ((pgd) + PTRS_PER_PGD)
 
-/*
- * We need to use the batch mode here, but pgd_pupulate() won't be
- * be called frequently.
- */
 static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, pud_t *pud)
 {
+	pgd_t ent = __pgd(_PAGE_TABLE | __pa(pud));
+
 	paravirt_alloc_pud(mm, __pa(pud) >> PAGE_SHIFT);
-	if (unlikely(PagePinned(virt_to_page((mm)->pgd)))) {
-		BUG_ON(HYPERVISOR_update_va_mapping(
-			       (unsigned long)pud,
-			       pfn_pte(virt_to_phys(pud)>>PAGE_SHIFT,
-				       PAGE_KERNEL_RO), 0));
-		set_pgd(pgd, __pgd(_PAGE_TABLE | __pa(pud)));
-		set_pgd(__user_pgd(pgd), __pgd(_PAGE_TABLE | __pa(pud)));
-	} else {
-		*(pgd) =  __pgd(_PAGE_TABLE | __pa(pud));
-		*__user_pgd(pgd) = *(pgd);
-	}
+	if (unlikely(PagePinned(virt_to_page(pgd))))
+		xen_l4_entry_update(pgd, 1, ent);
+	else
+		*__user_pgd(pgd) = *pgd = ent;
 }
 
 static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr)
--- head-2010-04-15.orig/arch/x86/include/mach-xen/asm/pgtable-3level.h	2010-03-24 15:25:06.000000000 +0100
+++ head-2010-04-15/arch/x86/include/mach-xen/asm/pgtable-3level.h	2010-03-25 14:41:00.000000000 +0100
@@ -61,12 +61,15 @@ static inline void __xen_pte_clear(pte_t
 	ptep->pte_high = 0;
 }
 
-static inline void xen_pmd_clear(pmd_t *pmd)
-{
-	xen_l2_entry_update(pmd, __pmd(0));
-}
+#define xen_pmd_clear(pmd)			\
+({						\
+	pmd_t *__pmdp = (pmd);			\
+	PagePinned(virt_to_page(__pmdp))	\
+	? set_pmd(__pmdp, __pmd(0))		\
+	: (void)(*__pmdp = __pmd(0));		\
+})
 
-static inline void pud_clear(pud_t *pudp)
+static inline void __xen_pud_clear(pud_t *pudp)
 {
 	pgdval_t pgd;
 
@@ -87,6 +90,14 @@ static inline void pud_clear(pud_t *pudp
 		xen_tlb_flush();
 }
 
+#define xen_pud_clear(pudp)			\
+({						\
+	pud_t *__pudp = (pudp);			\
+	PagePinned(virt_to_page(__pudp))	\
+	? __xen_pud_clear(__pudp)		\
+	: (void)(*__pudp = __pud(0));		\
+})
+
 #ifdef CONFIG_SMP
 static inline pte_t xen_ptep_get_and_clear(pte_t *ptep, pte_t res)
 {
--- head-2010-04-15.orig/arch/x86/include/mach-xen/asm/pgtable_64.h	2010-03-25 16:41:03.000000000 +0100
+++ head-2010-04-15/arch/x86/include/mach-xen/asm/pgtable_64.h	2010-03-25 14:41:00.000000000 +0100
@@ -79,33 +79,41 @@ static inline void xen_set_pmd(pmd_t *pm
 	xen_l2_entry_update(pmdp, pmd);
 }
 
-static inline void xen_pmd_clear(pmd_t *pmd)
-{
-	xen_set_pmd(pmd, xen_make_pmd(0));
-}
+#define xen_pmd_clear(pmd)			\
+({						\
+	pmd_t *__pmdp = (pmd);			\
+	PagePinned(virt_to_page(__pmdp))	\
+	? set_pmd(__pmdp, xen_make_pmd(0))	\
+	: (void)(*__pmdp = xen_make_pmd(0));	\
+})
 
 static inline void xen_set_pud(pud_t *pudp, pud_t pud)
 {
 	xen_l3_entry_update(pudp, pud);
 }
 
-static inline void xen_pud_clear(pud_t *pud)
-{
-	xen_set_pud(pud, xen_make_pud(0));
-}
+#define xen_pud_clear(pud)			\
+({						\
+	pud_t *__pudp = (pud);			\
+	PagePinned(virt_to_page(__pudp))	\
+	? set_pud(__pudp, xen_make_pud(0))	\
+	: (void)(*__pudp = xen_make_pud(0));	\
+})
 
 #define __user_pgd(pgd) ((pgd) + PTRS_PER_PGD)
 
 static inline void xen_set_pgd(pgd_t *pgdp, pgd_t pgd)
 {
-	xen_l4_entry_update(pgdp, pgd);
+	xen_l4_entry_update(pgdp, 0, pgd);
 }
 
-static inline void xen_pgd_clear(pgd_t *pgd)
-{
-	xen_set_pgd(pgd, xen_make_pgd(0));
-	xen_set_pgd(__user_pgd(pgd), xen_make_pgd(0));
-}
+#define xen_pgd_clear(pgd)			\
+({						\
+	pgd_t *__pgdp = (pgd);			\
+	PagePinned(virt_to_page(__pgdp))	\
+	? xen_l4_entry_update(__pgdp, 1, xen_make_pgd(0)) \
+	: (void)(*__user_pgd(__pgdp) = *__pgdp = xen_make_pgd(0)); \
+})
 
 #define __pte_mfn(_pte) (((_pte).pte & PTE_PFN_MASK) >> PAGE_SHIFT)
 
--- head-2010-04-15.orig/arch/x86/mm/hypervisor.c	2009-06-09 15:52:17.000000000 +0200
+++ head-2010-04-15/arch/x86/mm/hypervisor.c	2010-03-25 14:41:00.000000000 +0100
@@ -360,31 +360,91 @@ void xen_l1_entry_update(pte_t *ptr, pte
 }
 EXPORT_SYMBOL_GPL(xen_l1_entry_update);
 
+static void do_lN_entry_update(mmu_update_t *mmu, unsigned int mmu_count,
+                               struct page *page)
+{
+	if (likely(page)) {
+		multicall_entry_t mcl[2];
+		unsigned long pfn = page_to_pfn(page);
+
+		MULTI_update_va_mapping(mcl,
+					(unsigned long)__va(pfn << PAGE_SHIFT),
+					pfn_pte(pfn, PAGE_KERNEL_RO), 0);
+		SetPagePinned(page);
+		MULTI_mmu_update(mcl + 1, mmu, mmu_count, NULL, DOMID_SELF);
+		if (unlikely(HYPERVISOR_multicall_check(mcl, 2, NULL)))
+			BUG();
+	} else if (unlikely(HYPERVISOR_mmu_update(mmu, mmu_count,
+						  NULL, DOMID_SELF) < 0))
+		BUG();
+}
+
 void xen_l2_entry_update(pmd_t *ptr, pmd_t val)
 {
 	mmu_update_t u;
+	struct page *page = NULL;
+
+	if (likely(pmd_present(val)) && likely(!pmd_large(val))
+	    && likely(mem_map)
+	    && likely(PagePinned(virt_to_page(ptr)))) {
+		page = pmd_page(val);
+		if (unlikely(PagePinned(page)))
+			page = NULL;
+		else if (PageHighMem(page)) {
+#ifndef CONFIG_HIGHPTE
+			BUG();
+#endif
+			kmap_flush_unused();
+			page = NULL;
+		}
+	}
 	u.ptr = virt_to_machine(ptr);
 	u.val = __pmd_val(val);
-	BUG_ON(HYPERVISOR_mmu_update(&u, 1, NULL, DOMID_SELF) < 0);
+	do_lN_entry_update(&u, 1, page);
 }
 
 #if defined(CONFIG_X86_PAE) || defined(CONFIG_X86_64)
 void xen_l3_entry_update(pud_t *ptr, pud_t val)
 {
 	mmu_update_t u;
+	struct page *page = NULL;
+
+	if (likely(pud_present(val))
+#ifdef CONFIG_X86_64
+	    && likely(!pud_large(val))
+#endif
+	    && likely(mem_map)
+	    && likely(PagePinned(virt_to_page(ptr)))) {
+		page = pud_page(val);
+		if (unlikely(PagePinned(page)))
+			page = NULL;
+	}
 	u.ptr = virt_to_machine(ptr);
 	u.val = __pud_val(val);
-	BUG_ON(HYPERVISOR_mmu_update(&u, 1, NULL, DOMID_SELF) < 0);
+	do_lN_entry_update(&u, 1, page);
 }
 #endif
 
 #ifdef CONFIG_X86_64
-void xen_l4_entry_update(pgd_t *ptr, pgd_t val)
+void xen_l4_entry_update(pgd_t *ptr, int user, pgd_t val)
 {
-	mmu_update_t u;
-	u.ptr = virt_to_machine(ptr);
-	u.val = __pgd_val(val);
-	BUG_ON(HYPERVISOR_mmu_update(&u, 1, NULL, DOMID_SELF) < 0);
+	mmu_update_t u[2];
+	struct page *page = NULL;
+
+	if (likely(pgd_present(val)) && likely(mem_map)
+	    && likely(PagePinned(virt_to_page(ptr)))) {
+		page = pgd_page(val);
+		if (unlikely(PagePinned(page)))
+			page = NULL;
+	}
+	u[0].ptr = virt_to_machine(ptr);
+	u[0].val = __pgd_val(val);
+	if (user) {
+		u[1].ptr = virt_to_machine(__user_pgd(ptr));
+		u[1].val = __pgd_val(val);
+		do_lN_entry_update(u, 2, page);
+	} else
+		do_lN_entry_update(u, 1, page);
 }
 #endif /* CONFIG_X86_64 */
 
--- head-2010-04-15.orig/arch/x86/mm/init_32-xen.c	2010-03-25 14:37:41.000000000 +0100
+++ head-2010-04-15/arch/x86/mm/init_32-xen.c	2010-03-25 14:41:00.000000000 +0100
@@ -750,6 +750,8 @@ static void __init zone_sizes_init(void)
 #endif
 
 	free_area_init_nodes(max_zone_pfns);
+
+	xen_init_pgd_pin();
 }
 
 #ifndef CONFIG_NO_BOOTMEM
@@ -1028,8 +1030,6 @@ void __init mem_init(void)
 
 	save_pg_dir();
 	zap_low_mappings(true);
-
-	SetPagePinned(virt_to_page(init_mm.pgd));
 }
 
 #ifdef CONFIG_MEMORY_HOTPLUG
--- head-2010-04-15.orig/arch/x86/mm/init_64-xen.c	2010-04-15 11:41:27.000000000 +0200
+++ head-2010-04-15/arch/x86/mm/init_64-xen.c	2010-04-15 11:47:48.000000000 +0200
@@ -194,8 +194,11 @@ static pud_t *fill_pud(pgd_t *pgd, unsig
 {
 	if (pgd_none(*pgd)) {
 		pud_t *pud = (pud_t *)spp_getpage();
-		make_page_readonly(pud, XENFEAT_writable_page_tables);
-		pgd_populate(&init_mm, pgd, pud);
+		if (!after_bootmem) {
+			make_page_readonly(pud, XENFEAT_writable_page_tables);
+			xen_l4_entry_update(pgd, __pgd(__pa(pud) | _PAGE_TABLE));
+		} else
+			pgd_populate(&init_mm, pgd, pud);
 		if (pud != pud_offset(pgd, 0))
 			printk(KERN_ERR "PAGETABLE BUG #00! %p <-> %p\n",
 			       pud, pud_offset(pgd, 0));
@@ -207,8 +210,11 @@ static pmd_t *fill_pmd(pud_t *pud, unsig
 {
 	if (pud_none(*pud)) {
 		pmd_t *pmd = (pmd_t *) spp_getpage();
-		make_page_readonly(pmd, XENFEAT_writable_page_tables);
-		pud_populate(&init_mm, pud, pmd);
+		if (!after_bootmem) {
+			make_page_readonly(pmd, XENFEAT_writable_page_tables);
+			xen_l3_entry_update(pud, __pud(__pa(pmd) | _PAGE_TABLE));
+		} else
+			pud_populate(&init_mm, pud, pmd);
 		if (pmd != pmd_offset(pud, 0))
 			printk(KERN_ERR "PAGETABLE BUG #01! %p <-> %p\n",
 			       pmd, pmd_offset(pud, 0));
@@ -541,7 +547,6 @@ phys_pmd_init(pmd_t *pmd_page, unsigned 
 						   XENFEAT_writable_page_tables);
 			*pmd = __pmd(pte_phys | _PAGE_TABLE);
 		} else {
-			make_page_readonly(pte, XENFEAT_writable_page_tables);
 			spin_lock(&init_mm.page_table_lock);
 			pmd_populate_kernel(&init_mm, pmd, __va(pte_phys));
 			spin_unlock(&init_mm.page_table_lock);
@@ -630,7 +635,6 @@ phys_pud_init(pud_t *pud_page, unsigned 
 			else
 				*pud = __pud(pmd_phys | _PAGE_TABLE);
 		} else {
-			make_page_readonly(pmd, XENFEAT_writable_page_tables);
 			spin_lock(&init_mm.page_table_lock);
 			pud_populate(&init_mm, pud, __va(pmd_phys));
 			spin_unlock(&init_mm.page_table_lock);
@@ -804,7 +808,6 @@ kernel_physical_mapping_init(unsigned lo
 						   XENFEAT_writable_page_tables);
 			xen_l4_entry_update(pgd, __pgd(pud_phys | _PAGE_TABLE));
 		} else {
-			make_page_readonly(pud, XENFEAT_writable_page_tables);
 			spin_lock(&init_mm.page_table_lock);
 			pgd_populate(&init_mm, pgd, __va(pud_phys));
 			spin_unlock(&init_mm.page_table_lock);
@@ -869,7 +872,7 @@ void __init paging_init(void)
 
 	free_area_init_nodes(max_zone_pfns);
 
-	SetPagePinned(virt_to_page(init_mm.pgd));
+	xen_init_pgd_pin();
 }
 
 /*
--- head-2010-04-15.orig/arch/x86/mm/pgtable-xen.c	2010-04-15 10:53:40.000000000 +0200
+++ head-2010-04-15/arch/x86/mm/pgtable-xen.c	2010-04-15 11:47:53.000000000 +0200
@@ -66,16 +66,16 @@ early_param("userpte", setup_userpte);
 void __pte_free(pgtable_t pte)
 {
 	if (!PageHighMem(pte)) {
-		unsigned long va = (unsigned long)page_address(pte);
-		unsigned int level;
-		pte_t *ptep = lookup_address(va, &level);
-
-		BUG_ON(!ptep || level != PG_LEVEL_4K || !pte_present(*ptep));
-		if (!pte_write(*ptep)
-		    && HYPERVISOR_update_va_mapping(va,
-						    mk_pte(pte, PAGE_KERNEL),
-						    0))
-			BUG();
+		if (PagePinned(pte)) {
+			unsigned long pfn = page_to_pfn(pte);
+
+			if (HYPERVISOR_update_va_mapping((unsigned long)__va(pfn << PAGE_SHIFT),
+							 pfn_pte(pfn,
+								 PAGE_KERNEL),
+							 0))
+				BUG();
+			ClearPagePinned(pte);
+		}
 	} else
 #ifdef CONFIG_HIGHPTE
 		ClearPagePinned(pte);
@@ -117,14 +117,15 @@ pmd_t *pmd_alloc_one(struct mm_struct *m
 
 void __pmd_free(pgtable_t pmd)
 {
-	unsigned long va = (unsigned long)page_address(pmd);
-	unsigned int level;
-	pte_t *ptep = lookup_address(va, &level);
-
-	BUG_ON(!ptep || level != PG_LEVEL_4K || !pte_present(*ptep));
-	if (!pte_write(*ptep)
-	    && HYPERVISOR_update_va_mapping(va, mk_pte(pmd, PAGE_KERNEL), 0))
-		BUG();
+	if (PagePinned(pmd)) {
+		unsigned long pfn = page_to_pfn(pmd);
+
+		if (HYPERVISOR_update_va_mapping((unsigned long)__va(pfn << PAGE_SHIFT),
+						 pfn_pte(pfn, PAGE_KERNEL),
+						 0))
+			BUG();
+		ClearPagePinned(pmd);
+	}
 
 	ClearPageForeign(pmd);
 	init_page_count(pmd);
@@ -212,21 +213,20 @@ static inline unsigned int pgd_walk_set_
 {
 	unsigned long pfn = page_to_pfn(page);
 
-	if (PageHighMem(page)) {
-		if (pgprot_val(flags) & _PAGE_RW)
-			ClearPagePinned(page);
-		else
-			SetPagePinned(page);
-	} else {
-		MULTI_update_va_mapping(per_cpu(pb_mcl, cpu) + seq,
-					(unsigned long)__va(pfn << PAGE_SHIFT),
-					pfn_pte(pfn, flags), 0);
-		if (unlikely(++seq == PIN_BATCH)) {
-			if (unlikely(HYPERVISOR_multicall_check(per_cpu(pb_mcl, cpu),
-								PIN_BATCH, NULL)))
-				BUG();
-			seq = 0;
-		}
+	if (pgprot_val(flags) & _PAGE_RW)
+		ClearPagePinned(page);
+	else
+		SetPagePinned(page);
+	if (PageHighMem(page))
+		return seq;
+	MULTI_update_va_mapping(per_cpu(pb_mcl, cpu) + seq,
+				(unsigned long)__va(pfn << PAGE_SHIFT),
+				pfn_pte(pfn, flags), 0);
+	if (unlikely(++seq == PIN_BATCH)) {
+		if (unlikely(HYPERVISOR_multicall_check(per_cpu(pb_mcl, cpu),
+							PIN_BATCH, NULL)))
+			BUG();
+		seq = 0;
 	}
 
 	return seq;
@@ -273,6 +273,16 @@ static void pgd_walk(pgd_t *pgd_base, pg
 		}
 	}
 
+#ifdef CONFIG_X86_PAE
+	for (; g < PTRS_PER_PGD; g++, pgd++) {
+		BUG_ON(pgd_none(*pgd));
+		pud = pud_offset(pgd, 0);
+		BUG_ON(pud_none(*pud));
+		pmd = pmd_offset(pud, 0);
+		seq = pgd_walk_set_prot(virt_to_page(pmd),flags,cpu,seq);
+	}
+#endif
+
 	mcl = per_cpu(pb_mcl, cpu);
 #ifdef CONFIG_X86_64
 	if (unlikely(seq > PIN_BATCH - 2)) {
@@ -308,6 +318,51 @@ static void pgd_walk(pgd_t *pgd_base, pg
 	put_cpu();
 }
 
+void __init xen_init_pgd_pin(void)
+{
+	pgd_t       *pgd = init_mm.pgd;
+	pud_t       *pud;
+	pmd_t       *pmd;
+	unsigned int g, u, m;
+
+	if (xen_feature(XENFEAT_auto_translated_physmap))
+		return;
+
+	SetPagePinned(virt_to_page(pgd));
+	for (g = 0; g < PTRS_PER_PGD; g++, pgd++) {
+#ifndef CONFIG_X86_PAE
+		if (g >= pgd_index(HYPERVISOR_VIRT_START)
+		    && g <= pgd_index(HYPERVISOR_VIRT_END - 1))
+			continue;
+#endif
+		if (!pgd_present(*pgd))
+			continue;
+		pud = pud_offset(pgd, 0);
+		if (PTRS_PER_PUD > 1) /* not folded */
+			SetPagePinned(virt_to_page(pud));
+		for (u = 0; u < PTRS_PER_PUD; u++, pud++) {
+			if (!pud_present(*pud))
+				continue;
+			pmd = pmd_offset(pud, 0);
+			if (PTRS_PER_PMD > 1) /* not folded */
+				SetPagePinned(virt_to_page(pmd));
+			for (m = 0; m < PTRS_PER_PMD; m++, pmd++) {
+#ifdef CONFIG_X86_PAE
+				if (g == pgd_index(HYPERVISOR_VIRT_START)
+				    && m >= pmd_index(HYPERVISOR_VIRT_START))
+					continue;
+#endif
+				if (!pmd_present(*pmd))
+					continue;
+				SetPagePinned(pmd_page(*pmd));
+			}
+		}
+	}
+#ifdef CONFIG_X86_64
+	SetPagePinned(virt_to_page(level3_user_pgt));
+#endif
+}
+
 static void __pgd_pin(pgd_t *pgd)
 {
 	pgd_walk(pgd, PAGE_KERNEL_RO);
@@ -498,21 +553,18 @@ static void pgd_dtor(pgd_t *pgd)
 
 void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd)
 {
-	struct page *page = virt_to_page(pmd);
-	unsigned long pfn = page_to_pfn(page);
-
-	paravirt_alloc_pmd(mm, __pa(pmd) >> PAGE_SHIFT);
-
 	/* Note: almost everything apart from _PAGE_PRESENT is
 	   reserved at the pmd (PDPT) level. */
-	if (PagePinned(virt_to_page(mm->pgd))) {
-		BUG_ON(PageHighMem(page));
-		BUG_ON(HYPERVISOR_update_va_mapping(
-			  (unsigned long)__va(pfn << PAGE_SHIFT),
-			  pfn_pte(pfn, PAGE_KERNEL_RO), 0));
-		set_pud(pudp, __pud(__pa(pmd) | _PAGE_PRESENT));
-	} else
-		*pudp = __pud(__pa(pmd) | _PAGE_PRESENT);
+	pud_t pud = __pud(__pa(pmd) | _PAGE_PRESENT);
+
+	paravirt_alloc_pmd(mm, page_to_pfn(virt_to_page(pmd)));
+
+	if (likely(!PagePinned(virt_to_page(pudp)))) {
+		*pudp = pud;
+		return;
+	}
+
+	set_pud(pudp, pud);
 
 	/*
 	 * According to Intel App note "TLBs, Paging-Structure Caches,
@@ -607,13 +659,10 @@ static void pgd_prepopulate_pmd(struct m
 	     i++, pud++, addr += PUD_SIZE) {
 		pmd_t *pmd = pmds[i];
 
-		if (i >= KERNEL_PGD_BOUNDARY) {
+		if (i >= KERNEL_PGD_BOUNDARY)
 			memcpy(pmd,
 			       (pmd_t *)pgd_page_vaddr(swapper_pg_dir[i]),
 			       sizeof(pmd_t) * PTRS_PER_PMD);
-			make_lowmem_page_readonly(
-				pmd, XENFEAT_writable_page_tables);
-		}
 
 		/* It is safe to poke machine addresses of pmds under the pgd_lock. */
 		pud_populate(mm, pud, pmd);