Merge tag 'stable/for-linus-3.19-rc0b-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull additional xen update from David Vrabel:
 "Xen: additional features for 3.19-rc0

   - Linear p2m for x86 PV guests which simplifies the p2m code,
     improves performance and will allow for > 512 GB PV guests in the
     future.

  A last-minute, configuration specific issue was discovered with this
  change which is why it was not included in my previous pull request.
  This is now been fixed and tested"

* tag 'stable/for-linus-3.19-rc0b-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen: switch to post-init routines in xen mmu.c earlier
  Revert "swiotlb-xen: pass dev_addr to swiotlb_tbl_unmap_single"
  xen: annotate xen_set_identity_and_remap_chunk() with __init
  xen: introduce helper functions to do safe read and write accesses
  xen: Speed up set_phys_to_machine() by using read-only mappings
  xen: switch to linear virtual mapped sparse p2m list
  xen: Hide get_phys_to_machine() to be able to tune common path
  x86: Introduce function to get pmd entry pointer
  xen: Delay invalidating extra memory
  xen: Delay m2p_override initialization
  xen: Delay remapping memory of pv-domain
  xen: use common page allocation function in p2m.c
  xen: Make functions static
  xen: fix some style issues in p2m.c

4 files changed, 708 insertions, 951 deletions

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 8c8298d78185..5c1f9ace7ae7 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -387,7 +387,7 @@ static pteval_t pte_pfn_to_mfn(pteval_t val)
 		unsigned long mfn;
 
 		if (!xen_feature(XENFEAT_auto_translated_physmap))
-			mfn = get_phys_to_machine(pfn);
+			mfn = __pfn_to_mfn(pfn);
 		else
 			mfn = pfn;
 		/*
@@ -1113,20 +1113,16 @@ static void __init xen_cleanhighmap(unsigned long vaddr,
 	 * instead of somewhere later and be confusing. */
 	xen_mc_flush();
 }
-static void __init xen_pagetable_p2m_copy(void)
+
+static void __init xen_pagetable_p2m_free(void)
 {
 	unsigned long size;
 	unsigned long addr;
-	unsigned long new_mfn_list;
-
-	if (xen_feature(XENFEAT_auto_translated_physmap))
-		return;
 
 	size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
 
-	new_mfn_list = xen_revector_p2m_tree();
 	/* No memory or already called. */
-	if (!new_mfn_list || new_mfn_list == xen_start_info->mfn_list)
+	if ((unsigned long)xen_p2m_addr == xen_start_info->mfn_list)
 		return;
 
 	/* using __ka address and sticking INVALID_P2M_ENTRY! */
@@ -1144,8 +1140,6 @@ static void __init xen_pagetable_p2m_copy(void)
 
 	size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
 	memblock_free(__pa(xen_start_info->mfn_list), size);
-	/* And revector! Bye bye old array */
-	xen_start_info->mfn_list = new_mfn_list;
 
 	/* At this stage, cleanup_highmap has already cleaned __ka space
 	 * from _brk_limit way up to the max_pfn_mapped (which is the end of
@@ -1169,17 +1163,35 @@ static void __init xen_pagetable_p2m_copy(void)
 }
 #endif
 
-static void __init xen_pagetable_init(void)
+static void __init xen_pagetable_p2m_setup(void)
 {
-	paging_init();
+	if (xen_feature(XENFEAT_auto_translated_physmap))
+		return;
+
+	xen_vmalloc_p2m_tree();
+
 #ifdef CONFIG_X86_64
-	xen_pagetable_p2m_copy();
+	xen_pagetable_p2m_free();
 #endif
+	/* And revector! Bye bye old array */
+	xen_start_info->mfn_list = (unsigned long)xen_p2m_addr;
+}
+
+static void __init xen_pagetable_init(void)
+{
+	paging_init();
+	xen_post_allocator_init();
+
+	xen_pagetable_p2m_setup();
+
 	/* Allocate and initialize top and mid mfn levels for p2m structure */
 	xen_build_mfn_list_list();
 
+	/* Remap memory freed due to conflicts with E820 map */
+	if (!xen_feature(XENFEAT_auto_translated_physmap))
+		xen_remap_memory();
+
 	xen_setup_shared_info();
-	xen_post_allocator_init();
 }
 static void xen_write_cr2(unsigned long cr2)
 {
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index b456b048eca9..edbc7a63fd73 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -3,21 +3,22 @@
  * guests themselves, but it must also access and update the p2m array
  * during suspend/resume when all the pages are reallocated.
  *
- * The p2m table is logically a flat array, but we implement it as a
- * three-level tree to allow the address space to be sparse.
+ * The logical flat p2m table is mapped to a linear kernel memory area.
+ * For accesses by Xen a three-level tree linked via mfns only is set up to
+ * allow the address space to be sparse.
  *
- *                               Xen
- *                                |
- *     p2m_top              p2m_top_mfn
- *       /  \                   /   \
- * p2m_mid p2m_mid	p2m_mid_mfn p2m_mid_mfn
- *    / \      / \         /           /
- *  p2m p2m p2m p2m p2m p2m p2m ...
+ *               Xen
+ *                |
+ *          p2m_top_mfn
+ *              /   \
+ * p2m_mid_mfn p2m_mid_mfn
+ *         /           /
+ *  p2m p2m p2m ...
  *
  * The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.
  *
- * The p2m_top and p2m_top_mfn levels are limited to 1 page, so the
- * maximum representable pseudo-physical address space is:
+ * The p2m_top_mfn level is limited to 1 page, so the maximum representable
+ * pseudo-physical address space is:
  *  P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages
  *
  * P2M_PER_PAGE depends on the architecture, as a mfn is always
@@ -30,6 +31,9 @@
  * leaf entries, or for the top  root, or middle one, for which there is a void
  * entry, we assume it is  "missing". So (for example)
  *  pfn_to_mfn(0x90909090)=INVALID_P2M_ENTRY.
+ * We have a dedicated page p2m_missing with all entries being
+ * INVALID_P2M_ENTRY. This page may be referenced multiple times in the p2m
+ * list/tree in case there are multiple areas with P2M_PER_PAGE invalid pfns.
  *
  * We also have the possibility of setting 1-1 mappings on certain regions, so
  * that:
@@ -39,122 +43,20 @@
  * PCI BARs, or ACPI spaces), we can create mappings easily because we
  * get the PFN value to match the MFN.
  *
- * For this to work efficiently we have one new page p2m_identity and
- * allocate (via reserved_brk) any other pages we need to cover the sides
- * (1GB or 4MB boundary violations). All entries in p2m_identity are set to
- * INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs,
- * no other fancy value).
+ * For this to work efficiently we have one new page p2m_identity. All entries
+ * in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only
+ * recognizes that and MFNs, no other fancy value).
  *
  * On lookup we spot that the entry points to p2m_identity and return the
  * identity value instead of dereferencing and returning INVALID_P2M_ENTRY.
  * If the entry points to an allocated page, we just proceed as before and
- * return the PFN.  If the PFN has IDENTITY_FRAME_BIT set we unmask that in
+ * return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in
  * appropriate functions (pfn_to_mfn).
  *
  * The reason for having the IDENTITY_FRAME_BIT instead of just returning the
  * PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a
  * non-identity pfn. To protect ourselves against we elect to set (and get) the
  * IDENTITY_FRAME_BIT on all identity mapped PFNs.
- *
- * This simplistic diagram is used to explain the more subtle piece of code.
- * There is also a digram of the P2M at the end that can help.
- * Imagine your E820 looking as so:
- *
- *                    1GB                                           2GB    4GB
- * /-------------------+---------\/----\         /----------\    /---+-----\
- * | System RAM        | Sys RAM ||ACPI|         | reserved |    | Sys RAM |
- * \-------------------+---------/\----/         \----------/    \---+-----/
- *                               ^- 1029MB                       ^- 2001MB
- *
- * [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100),
- *  2048MB = 524288 (0x80000)]
- *
- * And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB
- * is actually not present (would have to kick the balloon driver to put it in).
- *
- * When we are told to set the PFNs for identity mapping (see patch: "xen/setup:
- * Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start
- * of the PFN and the end PFN (263424 and 512256 respectively). The first step
- * is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page
- * covers 512^2 of page estate (1GB) and in case the start or end PFN is not
- * aligned on 512^2*PAGE_SIZE (1GB) we reserve_brk new middle and leaf pages as
- * required to split any existing p2m_mid_missing middle pages.
- *
- * With the E820 example above, 263424 is not 1GB aligned so we allocate a
- * reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000.
- * Each entry in the allocate page is "missing" (points to p2m_missing).
- *
- * Next stage is to determine if we need to do a more granular boundary check
- * on the 4MB (or 2MB depending on architecture) off the start and end pfn's.
- * We check if the start pfn and end pfn violate that boundary check, and if
- * so reserve_brk a (p2m[x][y]) leaf page. This way we have a much finer
- * granularity of setting which PFNs are missing and which ones are identity.
- * In our example 263424 and 512256 both fail the check so we reserve_brk two
- * pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing"
- * values) and assign them to p2m[1][2] and p2m[1][488] respectively.
- *
- * At this point we would at minimum reserve_brk one page, but could be up to
- * three. Each call to set_phys_range_identity has at maximum a three page
- * cost. If we were to query the P2M at this stage, all those entries from
- * start PFN through end PFN (so 1029MB -> 2001MB) would return
- * INVALID_P2M_ENTRY ("missing").
- *
- * The next step is to walk from the start pfn to the end pfn setting
- * the IDENTITY_FRAME_BIT on each PFN. This is done in set_phys_range_identity.
- * If we find that the middle entry is pointing to p2m_missing we can swap it
- * over to p2m_identity - this way covering 4MB (or 2MB) PFN space (and
- * similarly swapping p2m_mid_missing for p2m_mid_identity for larger regions).
- * At this point we do not need to worry about boundary aligment (so no need to
- * reserve_brk a middle page, figure out which PFNs are "missing" and which
- * ones are identity), as that has been done earlier.  If we find that the
- * middle leaf is not occupied by p2m_identity or p2m_missing, we dereference
- * that page (which covers 512 PFNs) and set the appropriate PFN with
- * IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we
- * set from p2m[1][2][256->511] and p2m[1][488][0->256] with
- * IDENTITY_FRAME_BIT set.
- *
- * All other regions that are void (or not filled) either point to p2m_missing
- * (considered missing) or have the default value of INVALID_P2M_ENTRY (also
- * considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511]
- * contain the INVALID_P2M_ENTRY value and are considered "missing."
- *
- * Finally, the region beyond the end of of the E820 (4 GB in this example)
- * is set to be identity (in case there are MMIO regions placed here).
- *
- * This is what the p2m ends up looking (for the E820 above) with this
- * fabulous drawing:
- *
- *    p2m         /--------------\
- *  /-----\       | &mfn_list[0],|                           /-----------------\
- *  |  0  |------>| &mfn_list[1],|    /---------------\      | ~0, ~0, ..      |
- *  |-----|       |  ..., ~0, ~0 |    | ~0, ~0, [x]---+----->| IDENTITY [@256] |
- *  |  1  |---\   \--------------/    | [p2m_identity]+\     | IDENTITY [@257] |
- *  |-----|    \                      | [p2m_identity]+\\    | ....            |
- *  |  2  |--\  \-------------------->|  ...          | \\   \----------------/
- *  |-----|   \                       \---------------/  \\
- *  |  3  |-\  \                                          \\  p2m_identity [1]
- *  |-----|  \  \-------------------->/---------------\   /-----------------\
- *  | ..  |\  |                       | [p2m_identity]+-->| ~0, ~0, ~0, ... |
- *  \-----/ | |                       | [p2m_identity]+-->| ..., ~0         |
- *          | |                       | ....          |   \-----------------/
- *          | |                       +-[x], ~0, ~0.. +\
- *          | |                       \---------------/ \
- *          | |                                          \-> /---------------\
- *          | V  p2m_mid_missing       p2m_missing           | IDENTITY[@0]  |
- *          | /-----------------\     /------------\         | IDENTITY[@256]|
- *          | | [p2m_missing]   +---->| ~0, ~0, ...|         | ~0, ~0, ....  |
- *          | | [p2m_missing]   +---->| ..., ~0    |         \---------------/
- *          | | ...             |     \------------/
- *          | \-----------------/
- *          |
- *          |     p2m_mid_identity
- *          |   /-----------------\
- *          \-->| [p2m_identity]  +---->[1]
- *              | [p2m_identity]  +---->[1]
- *              | ...             |
- *              \-----------------/
- *
- * where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT)
  */
 
 #include <linux/init.h>
@@ -164,9 +66,11 @@
 #include <linux/sched.h>
 #include <linux/seq_file.h>
 #include <linux/bootmem.h>
+#include <linux/slab.h>
 
 #include <asm/cache.h>
 #include <asm/setup.h>
+#include <asm/uaccess.h>
 
 #include <asm/xen/page.h>
 #include <asm/xen/hypercall.h>
@@ -178,31 +82,26 @@
 #include "multicalls.h"
 #include "xen-ops.h"
 
+#define PMDS_PER_MID_PAGE	(P2M_MID_PER_PAGE / PTRS_PER_PTE)
+
 static void __init m2p_override_init(void);
 
+unsigned long *xen_p2m_addr __read_mostly;
+EXPORT_SYMBOL_GPL(xen_p2m_addr);
+unsigned long xen_p2m_size __read_mostly;
+EXPORT_SYMBOL_GPL(xen_p2m_size);
 unsigned long xen_max_p2m_pfn __read_mostly;
+EXPORT_SYMBOL_GPL(xen_max_p2m_pfn);
+
+static DEFINE_SPINLOCK(p2m_update_lock);
 
 static unsigned long *p2m_mid_missing_mfn;
 static unsigned long *p2m_top_mfn;
 static unsigned long **p2m_top_mfn_p;
-
-/* Placeholders for holes in the address space */
-static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE);
-static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE);
-
-static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE);
-
-static RESERVE_BRK_ARRAY(unsigned long, p2m_identity, P2M_PER_PAGE);
-static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_identity, P2M_MID_PER_PAGE);
-
-RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
-
-/* For each I/O range remapped we may lose up to two leaf pages for the boundary
- * violations and three mid pages to cover up to 3GB. With
- * early_can_reuse_p2m_middle() most of the leaf pages will be reused by the
- * remapped region.
- */
-RESERVE_BRK(p2m_identity_remap, PAGE_SIZE * 2 * 3 * MAX_REMAP_RANGES);
+static unsigned long *p2m_missing;
+static unsigned long *p2m_identity;
+static pte_t *p2m_missing_pte;
+static pte_t *p2m_identity_pte;
 
 static inline unsigned p2m_top_index(unsigned long pfn)
 {
@@ -220,14 +119,6 @@ static inline unsigned p2m_index(unsigned long pfn)
 	return pfn % P2M_PER_PAGE;
 }
 
-static void p2m_top_init(unsigned long ***top)
-{
-	unsigned i;
-
-	for (i = 0; i < P2M_TOP_PER_PAGE; i++)
-		top[i] = p2m_mid_missing;
-}
-
 static void p2m_top_mfn_init(unsigned long *top)
 {
 	unsigned i;
@@ -244,28 +135,43 @@ static void p2m_top_mfn_p_init(unsigned long **top)
 		top[i] = p2m_mid_missing_mfn;
 }
 
-static void p2m_mid_init(unsigned long **mid, unsigned long *leaf)
+static void p2m_mid_mfn_init(unsigned long *mid, unsigned long *leaf)
 {
 	unsigned i;
 
 	for (i = 0; i < P2M_MID_PER_PAGE; i++)
-		mid[i] = leaf;
+		mid[i] = virt_to_mfn(leaf);
 }
 
-static void p2m_mid_mfn_init(unsigned long *mid, unsigned long *leaf)
+static void p2m_init(unsigned long *p2m)
 {
 	unsigned i;
 
-	for (i = 0; i < P2M_MID_PER_PAGE; i++)
-		mid[i] = virt_to_mfn(leaf);
+	for (i = 0; i < P2M_PER_PAGE; i++)
+		p2m[i] = INVALID_P2M_ENTRY;
 }
 
-static void p2m_init(unsigned long *p2m)
+static void p2m_init_identity(unsigned long *p2m, unsigned long pfn)
 {
 	unsigned i;
 
-	for (i = 0; i < P2M_MID_PER_PAGE; i++)
-		p2m[i] = INVALID_P2M_ENTRY;
+	for (i = 0; i < P2M_PER_PAGE; i++)
+		p2m[i] = IDENTITY_FRAME(pfn + i);
+}
+
+static void * __ref alloc_p2m_page(void)
+{
+	if (unlikely(!slab_is_available()))
+		return alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
+
+	return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
+}
+
+/* Only to be called in case of a race for a page just allocated! */
+static void free_p2m_page(void *p)
+{
+	BUG_ON(!slab_is_available());
+	free_page((unsigned long)p);
 }
 
 /*
@@ -280,40 +186,46 @@ static void p2m_init(unsigned long *p2m)
  */
 void __ref xen_build_mfn_list_list(void)
 {
-	unsigned long pfn;
+	unsigned long pfn, mfn;
+	pte_t *ptep;
+	unsigned int level, topidx, mididx;
+	unsigned long *mid_mfn_p;
 
 	if (xen_feature(XENFEAT_auto_translated_physmap))
 		return;
 
 	/* Pre-initialize p2m_top_mfn to be completely missing */
 	if (p2m_top_mfn == NULL) {
-		p2m_mid_missing_mfn = alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
+		p2m_mid_missing_mfn = alloc_p2m_page();
 		p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
 
-		p2m_top_mfn_p = alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
+		p2m_top_mfn_p = alloc_p2m_page();
 		p2m_top_mfn_p_init(p2m_top_mfn_p);
 
-		p2m_top_mfn = alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
+		p2m_top_mfn = alloc_p2m_page();
 		p2m_top_mfn_init(p2m_top_mfn);
 	} else {
 		/* Reinitialise, mfn's all change after migration */
 		p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
 	}
 
-	for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) {
-		unsigned topidx = p2m_top_index(pfn);
-		unsigned mididx = p2m_mid_index(pfn);
-		unsigned long **mid;
-		unsigned long *mid_mfn_p;
+	for (pfn = 0; pfn < xen_max_p2m_pfn && pfn < MAX_P2M_PFN;
+	     pfn += P2M_PER_PAGE) {
+		topidx = p2m_top_index(pfn);
+		mididx = p2m_mid_index(pfn);
 
-		mid = p2m_top[topidx];
 		mid_mfn_p = p2m_top_mfn_p[topidx];
+		ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn),
+				      &level);
+		BUG_ON(!ptep || level != PG_LEVEL_4K);
+		mfn = pte_mfn(*ptep);
+		ptep = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
 
 		/* Don't bother allocating any mfn mid levels if
 		 * they're just missing, just update the stored mfn,
 		 * since all could have changed over a migrate.
 		 */
-		if (mid == p2m_mid_missing) {
+		if (ptep == p2m_missing_pte || ptep == p2m_identity_pte) {
 			BUG_ON(mididx);
 			BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
 			p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
@@ -322,19 +234,14 @@ void __ref xen_build_mfn_list_list(void)
 		}
 
 		if (mid_mfn_p == p2m_mid_missing_mfn) {
-			/*
-			 * XXX boot-time only!  We should never find
-			 * missing parts of the mfn tree after
-			 * runtime.
-			 */
-			mid_mfn_p = alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
+			mid_mfn_p = alloc_p2m_page();
 			p2m_mid_mfn_init(mid_mfn_p, p2m_missing);
 
 			p2m_top_mfn_p[topidx] = mid_mfn_p;
 		}
 
 		p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
-		mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]);
+		mid_mfn_p[mididx] = mfn;
 	}
 }
 
@@ -353,171 +260,235 @@ void xen_setup_mfn_list_list(void)
 /* Set up p2m_top to point to the domain-builder provided p2m pages */
 void __init xen_build_dynamic_phys_to_machine(void)
 {
-	unsigned long *mfn_list;
-	unsigned long max_pfn;
 	unsigned long pfn;
 
 	 if (xen_feature(XENFEAT_auto_translated_physmap))
 		return;
 
-	mfn_list = (unsigned long *)xen_start_info->mfn_list;
-	max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
-	xen_max_p2m_pfn = max_pfn;
+	xen_p2m_addr = (unsigned long *)xen_start_info->mfn_list;
+	xen_p2m_size = ALIGN(xen_start_info->nr_pages, P2M_PER_PAGE);
 
-	p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
-	p2m_init(p2m_missing);
-	p2m_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
-	p2m_init(p2m_identity);
+	for (pfn = xen_start_info->nr_pages; pfn < xen_p2m_size; pfn++)
+		xen_p2m_addr[pfn] = INVALID_P2M_ENTRY;
 
-	p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
-	p2m_mid_init(p2m_mid_missing, p2m_missing);
-	p2m_mid_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
-	p2m_mid_init(p2m_mid_identity, p2m_identity);
+	xen_max_p2m_pfn = xen_p2m_size;
+}
 
-	p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);
-	p2m_top_init(p2m_top);
+#define P2M_TYPE_IDENTITY	0
+#define P2M_TYPE_MISSING	1
+#define P2M_TYPE_PFN		2
+#define P2M_TYPE_UNKNOWN	3
 
-	/*
-	 * The domain builder gives us a pre-constructed p2m array in
-	 * mfn_list for all the pages initially given to us, so we just
-	 * need to graft that into our tree structure.
-	 */
-	for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) {
-		unsigned topidx = p2m_top_index(pfn);
-		unsigned mididx = p2m_mid_index(pfn);
+static int xen_p2m_elem_type(unsigned long pfn)
+{
+	unsigned long mfn;
 
-		if (p2m_top[topidx] == p2m_mid_missing) {
-			unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
-			p2m_mid_init(mid, p2m_missing);
+	if (pfn >= xen_p2m_size)
+		return P2M_TYPE_IDENTITY;
 
-			p2m_top[topidx] = mid;
-		}
+	mfn = xen_p2m_addr[pfn];
 
-		/*
-		 * As long as the mfn_list has enough entries to completely
-		 * fill a p2m page, pointing into the array is ok. But if
-		 * not the entries beyond the last pfn will be undefined.
-		 */
-		if (unlikely(pfn + P2M_PER_PAGE > max_pfn)) {
-			unsigned long p2midx;
+	if (mfn == INVALID_P2M_ENTRY)
+		return P2M_TYPE_MISSING;
 
-			p2midx = max_pfn % P2M_PER_PAGE;
-			for ( ; p2midx < P2M_PER_PAGE; p2midx++)
-				mfn_list[pfn + p2midx] = INVALID_P2M_ENTRY;
-		}
-		p2m_top[topidx][mididx] = &mfn_list[pfn];
-	}
+	if (mfn & IDENTITY_FRAME_BIT)
+		return P2M_TYPE_IDENTITY;
 
-	m2p_override_init();
+	return P2M_TYPE_PFN;
 }
-#ifdef CONFIG_X86_64
-unsigned long __init xen_revector_p2m_tree(void)
+
+static void __init xen_rebuild_p2m_list(unsigned long *p2m)
 {
-	unsigned long va_start;
-	unsigned long va_end;
+	unsigned int i, chunk;
 	unsigned long pfn;
-	unsigned long pfn_free = 0;
-	unsigned long *mfn_list = NULL;
-	unsigned long size;
-
-	va_start = xen_start_info->mfn_list;
-	/*We copy in increments of P2M_PER_PAGE * sizeof(unsigned long),
-	 * so make sure it is rounded up to that */
-	size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
-	va_end = va_start + size;
-
-	/* If we were revectored already, don't do it again. */
-	if (va_start <= __START_KERNEL_map && va_start >= __PAGE_OFFSET)
-		return 0;
+	unsigned long *mfns;
+	pte_t *ptep;
+	pmd_t *pmdp;
+	int type;
 
-	mfn_list = alloc_bootmem_align(size, PAGE_SIZE);
-	if (!mfn_list) {
-		pr_warn("Could not allocate space for a new P2M tree!\n");
-		return xen_start_info->mfn_list;
-	}
-	/* Fill it out with INVALID_P2M_ENTRY value */
-	memset(mfn_list, 0xFF, size);
+	p2m_missing = alloc_p2m_page();
+	p2m_init(p2m_missing);
+	p2m_identity = alloc_p2m_page();
+	p2m_init(p2m_identity);
 
-	for (pfn = 0; pfn < ALIGN(MAX_DOMAIN_PAGES, P2M_PER_PAGE); pfn += P2M_PER_PAGE) {
-		unsigned topidx = p2m_top_index(pfn);
-		unsigned mididx;
-		unsigned long *mid_p;
+	p2m_missing_pte = alloc_p2m_page();
+	paravirt_alloc_pte(&init_mm, __pa(p2m_missing_pte) >> PAGE_SHIFT);
+	p2m_identity_pte = alloc_p2m_page();
+	paravirt_alloc_pte(&init_mm, __pa(p2m_identity_pte) >> PAGE_SHIFT);
+	for (i = 0; i < PTRS_PER_PTE; i++) {
+		set_pte(p2m_missing_pte + i,
+			pfn_pte(PFN_DOWN(__pa(p2m_missing)), PAGE_KERNEL_RO));
+		set_pte(p2m_identity_pte + i,
+			pfn_pte(PFN_DOWN(__pa(p2m_identity)), PAGE_KERNEL_RO));
+	}
 
-		if (!p2m_top[topidx])
+	for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += chunk) {
+		/*
+		 * Try to map missing/identity PMDs or p2m-pages if possible.
+		 * We have to respect the structure of the mfn_list_list
+		 * which will be built just afterwards.
+		 * Chunk size to test is one p2m page if we are in the middle
+		 * of a mfn_list_list mid page and the complete mid page area
+		 * if we are at index 0 of the mid page. Please note that a
+		 * mid page might cover more than one PMD, e.g. on 32 bit PAE
+		 * kernels.
+		 */
+		chunk = (pfn & (P2M_PER_PAGE * P2M_MID_PER_PAGE - 1)) ?
+			P2M_PER_PAGE : P2M_PER_PAGE * P2M_MID_PER_PAGE;
+
+		type = xen_p2m_elem_type(pfn);
+		i = 0;
+		if (type != P2M_TYPE_PFN)
+			for (i = 1; i < chunk; i++)
+				if (xen_p2m_elem_type(pfn + i) != type)
+					break;
+		if (i < chunk)
+			/* Reset to minimal chunk size. */
+			chunk = P2M_PER_PAGE;
+
+		if (type == P2M_TYPE_PFN || i < chunk) {
+			/* Use initial p2m page contents. */
+#ifdef CONFIG_X86_64
+			mfns = alloc_p2m_page();
+			copy_page(mfns, xen_p2m_addr + pfn);
+#else
+			mfns = xen_p2m_addr + pfn;
+#endif
+			ptep = populate_extra_pte((unsigned long)(p2m + pfn));
+			set_pte(ptep,
+				pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL));
 			continue;
+		}
 
-		if (p2m_top[topidx] == p2m_mid_missing)
+		if (chunk == P2M_PER_PAGE) {
+			/* Map complete missing or identity p2m-page. */
+			mfns = (type == P2M_TYPE_MISSING) ?
+				p2m_missing : p2m_identity;
+			ptep = populate_extra_pte((unsigned long)(p2m + pfn));
+			set_pte(ptep,
+				pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL_RO));
 			continue;
+		}
 
-		mididx = p2m_mid_index(pfn);
-		mid_p = p2m_top[topidx][mididx];
-		if (!mid_p)
-			continue;
-		if ((mid_p == p2m_missing) || (mid_p == p2m_identity))
-			continue;
+		/* Complete missing or identity PMD(s) can be mapped. */
+		ptep = (type == P2M_TYPE_MISSING) ?
+			p2m_missing_pte : p2m_identity_pte;
+		for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
+			pmdp = populate_extra_pmd(
+				(unsigned long)(p2m + pfn + i * PTRS_PER_PTE));
+			set_pmd(pmdp, __pmd(__pa(ptep) | _KERNPG_TABLE));
+		}
+	}
+}
 
-		if ((unsigned long)mid_p == INVALID_P2M_ENTRY)
-			continue;
+void __init xen_vmalloc_p2m_tree(void)
+{
+	static struct vm_struct vm;
 
-		/* The old va. Rebase it on mfn_list */
-		if (mid_p >= (unsigned long *)va_start && mid_p <= (unsigned long *)va_end) {
-			unsigned long *new;
+	vm.flags = VM_ALLOC;
+	vm.size = ALIGN(sizeof(unsigned long) * xen_max_p2m_pfn,
+			PMD_SIZE * PMDS_PER_MID_PAGE);
+	vm_area_register_early(&vm, PMD_SIZE * PMDS_PER_MID_PAGE);
+	pr_notice("p2m virtual area at %p, size is %lx\n", vm.addr, vm.size);
 
-			if (pfn_free  > (size / sizeof(unsigned long))) {
-				WARN(1, "Only allocated for %ld pages, but we want %ld!\n",
-				     size / sizeof(unsigned long), pfn_free);
-				return 0;
-			}
-			new = &mfn_list[pfn_free];
+	xen_max_p2m_pfn = vm.size / sizeof(unsigned long);
 
-			copy_page(new, mid_p);
-			p2m_top[topidx][mididx] = &mfn_list[pfn_free];
+	xen_rebuild_p2m_list(vm.addr);
 
-			pfn_free += P2M_PER_PAGE;
+	xen_p2m_addr = vm.addr;
+	xen_p2m_size = xen_max_p2m_pfn;
 
-		}
-		/* This should be the leafs allocated for identity from _brk. */
-	}
-	return (unsigned long)mfn_list;
+	xen_inv_extra_mem();
 
+	m2p_override_init();
 }
-#else
-unsigned long __init xen_revector_p2m_tree(void)
-{
-	return 0;
-}
-#endif
+
 unsigned long get_phys_to_machine(unsigned long pfn)
 {
-	unsigned topidx, mididx, idx;
+	pte_t *ptep;
+	unsigned int level;
+
+	if (unlikely(pfn >= xen_p2m_size)) {
+		if (pfn < xen_max_p2m_pfn)
+			return xen_chk_extra_mem(pfn);
 
-	if (unlikely(pfn >= MAX_P2M_PFN))
 		return IDENTITY_FRAME(pfn);
+	}
 
-	topidx = p2m_top_index(pfn);
-	mididx = p2m_mid_index(pfn);
-	idx = p2m_index(pfn);
+	ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
+	BUG_ON(!ptep || level != PG_LEVEL_4K);
 
 	/*
 	 * The INVALID_P2M_ENTRY is filled in both p2m_*identity
 	 * and in p2m_*missing, so returning the INVALID_P2M_ENTRY
 	 * would be wrong.
 	 */
-	if (p2m_top[topidx][mididx] == p2m_identity)
+	if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
 		return IDENTITY_FRAME(pfn);
 
-	return p2m_top[topidx][mididx][idx];
+	return xen_p2m_addr[pfn];
 }
 EXPORT_SYMBOL_GPL(get_phys_to_machine);
 
-static void *alloc_p2m_page(void)
+/*
+ * Allocate new pmd(s). It is checked whether the old pmd is still in place.
+ * If not, nothing is changed. This is okay as the only reason for allocating
+ * a new pmd is to replace p2m_missing_pte or p2m_identity_pte by a individual
+ * pmd. In case of PAE/x86-32 there are multiple pmds to allocate!
+ */
+static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *ptep, pte_t *pte_pg)
 {
-	return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
-}
+	pte_t *ptechk;
+	pte_t *pteret = ptep;
+	pte_t *pte_newpg[PMDS_PER_MID_PAGE];
+	pmd_t *pmdp;
+	unsigned int level;
+	unsigned long flags;
+	unsigned long vaddr;
+	int i;
 
-static void free_p2m_page(void *p)
-{
-	free_page((unsigned long)p);
+	/* Do all allocations first to bail out in error case. */
+	for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
+		pte_newpg[i] = alloc_p2m_page();
+		if (!pte_newpg[i]) {
+			for (i--; i >= 0; i--)
+				free_p2m_page(pte_newpg[i]);
+
+			return NULL;
+		}
+	}
+
+	vaddr = addr & ~(PMD_SIZE * PMDS_PER_MID_PAGE - 1);
+
+	for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
+		copy_page(pte_newpg[i], pte_pg);
+		paravirt_alloc_pte(&init_mm, __pa(pte_newpg[i]) >> PAGE_SHIFT);
+
+		pmdp = lookup_pmd_address(vaddr);
+		BUG_ON(!pmdp);
+
+		spin_lock_irqsave(&p2m_update_lock, flags);
+
+		ptechk = lookup_address(vaddr, &level);
+		if (ptechk == pte_pg) {
+			set_pmd(pmdp,
+				__pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE));
+			if (vaddr == (addr & ~(PMD_SIZE - 1)))
+				pteret = pte_offset_kernel(pmdp, addr);
+			pte_newpg[i] = NULL;
+		}
+
+		spin_unlock_irqrestore(&p2m_update_lock, flags);
+
+		if (pte_newpg[i]) {
+			paravirt_release_pte(__pa(pte_newpg[i]) >> PAGE_SHIFT);
+			free_p2m_page(pte_newpg[i]);
+		}
+
+		vaddr += PMD_SIZE;
+	}
+
+	return pteret;
 }
 
 /*
@@ -530,58 +501,62 @@ static void free_p2m_page(void *p)
 static bool alloc_p2m(unsigned long pfn)
 {
 	unsigned topidx, mididx;
-	unsigned long ***top_p, **mid;
 	unsigned long *top_mfn_p, *mid_mfn;
-	unsigned long *p2m_orig;
+	pte_t *ptep, *pte_pg;
+	unsigned int level;
+	unsigned long flags;
+	unsigned long addr = (unsigned long)(xen_p2m_addr + pfn);
+	unsigned long p2m_pfn;
 
 	topidx = p2m_top_index(pfn);
 	mididx = p2m_mid_index(pfn);
 
-	top_p = &p2m_top[topidx];
-	mid = ACCESS_ONCE(*top_p);
+	ptep = lookup_address(addr, &level);
+	BUG_ON(!ptep || level != PG_LEVEL_4K);
+	pte_pg = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
 
-	if (mid == p2m_mid_missing) {
-		/* Mid level is missing, allocate a new one */
-		mid = alloc_p2m_page();
-		if (!mid)
+	if (pte_pg == p2m_missing_pte || pte_pg == p2m_identity_pte) {
+		/* PMD level is missing, allocate a new one */
+		ptep = alloc_p2m_pmd(addr, ptep, pte_pg);
+		if (!ptep)
 			return false;
-
-		p2m_mid_init(mid, p2m_missing);
-
-		if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing)
-			free_p2m_page(mid);
 	}
 
-	top_mfn_p = &p2m_top_mfn[topidx];
-	mid_mfn = ACCESS_ONCE(p2m_top_mfn_p[topidx]);
+	if (p2m_top_mfn) {
+		top_mfn_p = &p2m_top_mfn[topidx];
+		mid_mfn = ACCESS_ONCE(p2m_top_mfn_p[topidx]);
 
-	BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
+		BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
 
-	if (mid_mfn == p2m_mid_missing_mfn) {
-		/* Separately check the mid mfn level */
-		unsigned long missing_mfn;
-		unsigned long mid_mfn_mfn;
-		unsigned long old_mfn;
+		if (mid_mfn == p2m_mid_missing_mfn) {
+			/* Separately check the mid mfn level */
+			unsigned long missing_mfn;
+			unsigned long mid_mfn_mfn;
+			unsigned long old_mfn;
 
-		mid_mfn = alloc_p2m_page();
-		if (!mid_mfn)
-			return false;
+			mid_mfn = alloc_p2m_page();
+			if (!mid_mfn)
+				return false;
 
-		p2m_mid_mfn_init(mid_mfn, p2m_missing);
+			p2m_mid_mfn_init(mid_mfn, p2m_missing);
 
-		missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
-		mid_mfn_mfn = virt_to_mfn(mid_mfn);
-		old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn);
-		if (old_mfn != missing_mfn) {
-			free_p2m_page(mid_mfn);
-			mid_mfn = mfn_to_virt(old_mfn);
-		} else {
-			p2m_top_mfn_p[topidx] = mid_mfn;
+			missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
+			mid_mfn_mfn = virt_to_mfn(mid_mfn);
+			old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn);
+			if (old_mfn != missing_mfn) {
+				free_p2m_page(mid_mfn);
+				mid_mfn = mfn_to_virt(old_mfn);
+			} else {
+				p2m_top_mfn_p[topidx] = mid_mfn;
+			}
 		}
+	} else {
+		mid_mfn = NULL;
 	}
 
-	p2m_orig = ACCESS_ONCE(p2m_top[topidx][mididx]);
-	if (p2m_orig == p2m_identity || p2m_orig == p2m_missing) {
+	p2m_pfn = pte_pfn(ACCESS_ONCE(*ptep));
+	if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) ||
+	    p2m_pfn == PFN_DOWN(__pa(p2m_missing))) {
 		/* p2m leaf page is missing */
 		unsigned long *p2m;
 
@@ -589,183 +564,36 @@ static bool alloc_p2m(unsigned long pfn)
 		if (!p2m)
 			return false;
 
-		p2m_init(p2m);
-
-		if (cmpxchg(&mid[mididx], p2m_orig, p2m) != p2m_orig)
-			free_p2m_page(p2m);
+		if (p2m_pfn == PFN_DOWN(__pa(p2m_missing)))
+			p2m_init(p2m);
 		else
-			mid_mfn[mididx] = virt_to_mfn(p2m);
-	}
-
-	return true;
-}
-
-static bool __init early_alloc_p2m(unsigned long pfn, bool check_boundary)
-{
-	unsigned topidx, mididx, idx;
-	unsigned long *p2m;
-
-	topidx = p2m_top_index(pfn);
-	mididx = p2m_mid_index(pfn);
-	idx = p2m_index(pfn);
-
-	/* Pfff.. No boundary cross-over, lets get out. */
-	if (!idx && check_boundary)
-		return false;
-
-	WARN(p2m_top[topidx][mididx] == p2m_identity,
-		"P2M[%d][%d] == IDENTITY, should be MISSING (or alloced)!\n",
-		topidx, mididx);
-
-	/*
-	 * Could be done by xen_build_dynamic_phys_to_machine..
-	 */
-	if (p2m_top[topidx][mididx] != p2m_missing)
-		return false;
-
-	/* Boundary cross-over for the edges: */
-	p2m = extend_brk(PAGE_SIZE, PAGE_SIZE);
-
-	p2m_init(p2m);
+			p2m_init_identity(p2m, pfn);
 
-	p2m_top[topidx][mididx] = p2m;
+		spin_lock_irqsave(&p2m_update_lock, flags);
 
-	return true;
-}
-
-static bool __init early_alloc_p2m_middle(unsigned long pfn)
-{
-	unsigned topidx = p2m_top_index(pfn);
-	unsigned long **mid;
-
-	mid = p2m_top[topidx];
-	if (mid == p2m_mid_missing) {
-		mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
-
-		p2m_mid_init(mid, p2m_missing);
-
-		p2m_top[topidx] = mid;
-	}
-	return true;
-}
-
-/*
- * Skim over the P2M tree looking at pages that are either filled with
- * INVALID_P2M_ENTRY or with 1:1 PFNs. If found, re-use that page and
- * replace the P2M leaf with a p2m_missing or p2m_identity.
- * Stick the old page in the new P2M tree location.
- */
-static bool __init early_can_reuse_p2m_middle(unsigned long set_pfn)
-{
-	unsigned topidx;
-	unsigned mididx;
-	unsigned ident_pfns;
-	unsigned inv_pfns;
-	unsigned long *p2m;
-	unsigned idx;
-	unsigned long pfn;
-
-	/* We only look when this entails a P2M middle layer */
-	if (p2m_index(set_pfn))
-		return false;
-
-	for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn += P2M_PER_PAGE) {
-		topidx = p2m_top_index(pfn);
-
-		if (!p2m_top[topidx])
-			continue;
-
-		if (p2m_top[topidx] == p2m_mid_missing)
-			continue;
-
-		mididx = p2m_mid_index(pfn);
-		p2m = p2m_top[topidx][mididx];
-		if (!p2m)
-			continue;
-
-		if ((p2m == p2m_missing) || (p2m == p2m_identity))
-			continue;
-
-		if ((unsigned long)p2m == INVALID_P2M_ENTRY)
-			continue;
-
-		ident_pfns = 0;
-		inv_pfns = 0;
-		for (idx = 0; idx < P2M_PER_PAGE; idx++) {
-			/* IDENTITY_PFNs are 1:1 */
-			if (p2m[idx] == IDENTITY_FRAME(pfn + idx))
-				ident_pfns++;
-			else if (p2m[idx] == INVALID_P2M_ENTRY)
-				inv_pfns++;
-			else
-				break;
+		if (pte_pfn(*ptep) == p2m_pfn) {
+			set_pte(ptep,
+				pfn_pte(PFN_DOWN(__pa(p2m)), PAGE_KERNEL));
+			if (mid_mfn)
+				mid_mfn[mididx] = virt_to_mfn(p2m);
+			p2m = NULL;
 		}
-		if ((ident_pfns == P2M_PER_PAGE) || (inv_pfns == P2M_PER_PAGE))
-			goto found;
-	}
-	return false;
-found:
-	/* Found one, replace old with p2m_identity or p2m_missing */
-	p2m_top[topidx][mididx] = (ident_pfns ? p2m_identity : p2m_missing);
-
-	/* Reset where we want to stick the old page in. */
-	topidx = p2m_top_index(set_pfn);
-	mididx = p2m_mid_index(set_pfn);
-
-	/* This shouldn't happen */
-	if (WARN_ON(p2m_top[topidx] == p2m_mid_missing))
-		early_alloc_p2m_middle(set_pfn);
-
-	if (WARN_ON(p2m_top[topidx][mididx] != p2m_missing))
-		return false;
-
-	p2m_init(p2m);
-	p2m_top[topidx][mididx] = p2m;
 
-	return true;
-}
-bool __init early_set_phys_to_machine(unsigned long pfn, unsigned long mfn)
-{
-	if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {
-		if (!early_alloc_p2m_middle(pfn))
-			return false;
-
-		if (early_can_reuse_p2m_middle(pfn))
-			return __set_phys_to_machine(pfn, mfn);
-
-		if (!early_alloc_p2m(pfn, false /* boundary crossover OK!*/))
-			return false;
+		spin_unlock_irqrestore(&p2m_update_lock, flags);
 
-		if (!__set_phys_to_machine(pfn, mfn))
-			return false;
+		if (p2m)
+			free_p2m_page(p2m);
 	}
 
 	return true;
 }
 
-static void __init early_split_p2m(unsigned long pfn)
-{
-	unsigned long mididx, idx;
-
-	mididx = p2m_mid_index(pfn);
-	idx = p2m_index(pfn);
-
-	/*
-	 * Allocate new middle and leaf pages if this pfn lies in the
-	 * middle of one.
-	 */
-	if (mididx || idx)
-		early_alloc_p2m_middle(pfn);
-	if (idx)
-		early_alloc_p2m(pfn, false);
-}
-
 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
 				      unsigned long pfn_e)
 {
 	unsigned long pfn;
 
-	if (unlikely(pfn_s >= MAX_P2M_PFN))
+	if (unlikely(pfn_s >= xen_p2m_size))
 		return 0;
 
 	if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
@@ -774,101 +602,51 @@ unsigned long __init set_phys_range_identity(unsigned long pfn_s,
 	if (pfn_s > pfn_e)
 		return 0;
 
-	if (pfn_e > MAX_P2M_PFN)
-		pfn_e = MAX_P2M_PFN;
-
-	early_split_p2m(pfn_s);
-	early_split_p2m(pfn_e);
-
-	for (pfn = pfn_s; pfn < pfn_e;) {
-		unsigned topidx = p2m_top_index(pfn);
-		unsigned mididx = p2m_mid_index(pfn);
-
-		if (!__set_phys_to_machine(pfn, IDENTITY_FRAME(pfn)))
-			break;
-		pfn++;
-
-		/*
-		 * If the PFN was set to a middle or leaf identity
-		 * page the remainder must also be identity, so skip
-		 * ahead to the next middle or leaf entry.
-		 */
-		if (p2m_top[topidx] == p2m_mid_identity)
-			pfn = ALIGN(pfn, P2M_MID_PER_PAGE * P2M_PER_PAGE);
-		else if (p2m_top[topidx][mididx] == p2m_identity)
-			pfn = ALIGN(pfn, P2M_PER_PAGE);
-	}
+	if (pfn_e > xen_p2m_size)
+		pfn_e = xen_p2m_size;
 
-	WARN((pfn - pfn_s) != (pfn_e - pfn_s),
-		"Identity mapping failed. We are %ld short of 1-1 mappings!\n",
-		(pfn_e - pfn_s) - (pfn - pfn_s));
+	for (pfn = pfn_s; pfn < pfn_e; pfn++)
+		xen_p2m_addr[pfn] = IDENTITY_FRAME(pfn);
 
 	return pfn - pfn_s;
 }
 
-/* Try to install p2m mapping; fail if intermediate bits missing */
 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 {
-	unsigned topidx, mididx, idx;
+	pte_t *ptep;
+	unsigned int level;
 
 	/* don't track P2M changes in autotranslate guests */
 	if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
 		return true;
 
-	if (unlikely(pfn >= MAX_P2M_PFN)) {
+	if (unlikely(pfn >= xen_p2m_size)) {
 		BUG_ON(mfn != INVALID_P2M_ENTRY);
 		return true;
 	}
 
-	topidx = p2m_top_index(pfn);
-	mididx = p2m_mid_index(pfn);
-	idx = p2m_index(pfn);
-
-	/* For sparse holes were the p2m leaf has real PFN along with
-	 * PCI holes, stick in the PFN as the MFN value.
-	 *
-	 * set_phys_range_identity() will have allocated new middle
-	 * and leaf pages as required so an existing p2m_mid_missing
-	 * or p2m_missing mean that whole range will be identity so
-	 * these can be switched to p2m_mid_identity or p2m_identity.
-	 */
-	if (mfn != INVALID_P2M_ENTRY && (mfn & IDENTITY_FRAME_BIT)) {
-		if (p2m_top[topidx] == p2m_mid_identity)
-			return true;
-
-		if (p2m_top[topidx] == p2m_mid_missing) {
-			WARN_ON(cmpxchg(&p2m_top[topidx], p2m_mid_missing,
-					p2m_mid_identity) != p2m_mid_missing);
-			return true;
-		}
-
-		if (p2m_top[topidx][mididx] == p2m_identity)
-			return true;
+	if (likely(!xen_safe_write_ulong(xen_p2m_addr + pfn, mfn)))
+		return true;
 
-		/* Swap over from MISSING to IDENTITY if needed. */
-		if (p2m_top[topidx][mididx] == p2m_missing) {
-			WARN_ON(cmpxchg(&p2m_top[topidx][mididx], p2m_missing,
-				p2m_identity) != p2m_missing);
-			return true;
-		}
-	}
+	ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
+	BUG_ON(!ptep || level != PG_LEVEL_4K);
 
-	if (p2m_top[topidx][mididx] == p2m_missing)
+	if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_missing)))
 		return mfn == INVALID_P2M_ENTRY;
 
-	p2m_top[topidx][mididx][idx] = mfn;
+	if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
+		return mfn == IDENTITY_FRAME(pfn);
 
-	return true;
+	return false;
 }
 
 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 {
-	if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {
+	if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
 		if (!alloc_p2m(pfn))
 			return false;
 
-		if (!__set_phys_to_machine(pfn, mfn))
-			return false;
+		return __set_phys_to_machine(pfn, mfn);
 	}
 
 	return true;
@@ -877,15 +655,16 @@ bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 #define M2P_OVERRIDE_HASH_SHIFT	10
 #define M2P_OVERRIDE_HASH	(1 << M2P_OVERRIDE_HASH_SHIFT)
 
-static RESERVE_BRK_ARRAY(struct list_head, m2p_overrides, M2P_OVERRIDE_HASH);
+static struct list_head *m2p_overrides;
 static DEFINE_SPINLOCK(m2p_override_lock);
 
 static void __init m2p_override_init(void)
 {
 	unsigned i;
 
-	m2p_overrides = extend_brk(sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH,
-				   sizeof(unsigned long));
+	m2p_overrides = alloc_bootmem_align(
+				sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH,
+				sizeof(unsigned long));
 
 	for (i = 0; i < M2P_OVERRIDE_HASH; i++)
 		INIT_LIST_HEAD(&m2p_overrides[i]);
@@ -896,68 +675,9 @@ static unsigned long mfn_hash(unsigned long mfn)
 	return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT);
 }
 
-int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
-			    struct gnttab_map_grant_ref *kmap_ops,
-			    struct page **pages, unsigned int count)
-{
-	int i, ret = 0;
-	bool lazy = false;
-	pte_t *pte;
-
-	if (xen_feature(XENFEAT_auto_translated_physmap))
-		return 0;
-
-	if (kmap_ops &&
-	    !in_interrupt() &&
-	    paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
-		arch_enter_lazy_mmu_mode();
-		lazy = true;
-	}
-
-	for (i = 0; i < count; i++) {
-		unsigned long mfn, pfn;
-
-		/* Do not add to override if the map failed. */
-		if (map_ops[i].status)
-			continue;
-
-		if (map_ops[i].flags & GNTMAP_contains_pte) {
-			pte = (pte_t *) (mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
-				(map_ops[i].host_addr & ~PAGE_MASK));
-			mfn = pte_mfn(*pte);
-		} else {
-			mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
-		}
-		pfn = page_to_pfn(pages[i]);
-
-		WARN_ON(PagePrivate(pages[i]));
-		SetPagePrivate(pages[i]);
-		set_page_private(pages[i], mfn);
-		pages[i]->index = pfn_to_mfn(pfn);
-
-		if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
-			ret = -ENOMEM;
-			goto out;
-		}
-
-		if (kmap_ops) {
-			ret = m2p_add_override(mfn, pages[i], &kmap_ops[i]);
-			if (ret)
-				goto out;
-		}
-	}
-
-out:
-	if (lazy)
-		arch_leave_lazy_mmu_mode();
-
-	return ret;
-}
-EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
-
 /* Add an MFN override for a particular page */
-int m2p_add_override(unsigned long mfn, struct page *page,
-		struct gnttab_map_grant_ref *kmap_op)
+static int m2p_add_override(unsigned long mfn, struct page *page,
+			    struct gnttab_map_grant_ref *kmap_op)
 {
 	unsigned long flags;
 	unsigned long pfn;
@@ -970,7 +690,7 @@ int m2p_add_override(unsigned long mfn, struct page *page,
 		address = (unsigned long)__va(pfn << PAGE_SHIFT);
 		ptep = lookup_address(address, &level);
 		if (WARN(ptep == NULL || level != PG_LEVEL_4K,
-					"m2p_add_override: pfn %lx not mapped", pfn))
+			 "m2p_add_override: pfn %lx not mapped", pfn))
 			return -EINVAL;
 	}
 
@@ -1004,19 +724,19 @@ int m2p_add_override(unsigned long mfn, struct page *page,
 	 * because mfn_to_pfn (that ends up being called by GUPF) will
 	 * return the backend pfn rather than the frontend pfn. */
 	pfn = mfn_to_pfn_no_overrides(mfn);
-	if (get_phys_to_machine(pfn) == mfn)
+	if (__pfn_to_mfn(pfn) == mfn)
 		set_phys_to_machine(pfn, FOREIGN_FRAME(mfn));
 
 	return 0;
 }
-EXPORT_SYMBOL_GPL(m2p_add_override);
 
-int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
-			      struct gnttab_map_grant_ref *kmap_ops,
-			      struct page **pages, unsigned int count)
+int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
+			    struct gnttab_map_grant_ref *kmap_ops,
+			    struct page **pages, unsigned int count)
 {
 	int i, ret = 0;
 	bool lazy = false;
+	pte_t *pte;
 
 	if (xen_feature(XENFEAT_auto_translated_physmap))
 		return 0;
@@ -1029,35 +749,75 @@ int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
 	}
 
 	for (i = 0; i < count; i++) {
-		unsigned long mfn = get_phys_to_machine(page_to_pfn(pages[i]));
-		unsigned long pfn = page_to_pfn(pages[i]);
+		unsigned long mfn, pfn;
 
-		if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
-			ret = -EINVAL;
-			goto out;
+		/* Do not add to override if the map failed. */
+		if (map_ops[i].status)
+			continue;
+
+		if (map_ops[i].flags & GNTMAP_contains_pte) {
+			pte = (pte_t *)(mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
+				(map_ops[i].host_addr & ~PAGE_MASK));
+			mfn = pte_mfn(*pte);
+		} else {
+			mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
 		}
+		pfn = page_to_pfn(pages[i]);
 
-		set_page_private(pages[i], INVALID_P2M_ENTRY);
-		WARN_ON(!PagePrivate(pages[i]));
-		ClearPagePrivate(pages[i]);
-		set_phys_to_machine(pfn, pages[i]->index);
+		WARN_ON(PagePrivate(pages[i]));
+		SetPagePrivate(pages[i]);
+		set_page_private(pages[i], mfn);
+		pages[i]->index = pfn_to_mfn(pfn);
 
-		if (kmap_ops)
-			ret = m2p_remove_override(pages[i], &kmap_ops[i], mfn);
-		if (ret)
+		if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
+			ret = -ENOMEM;
 			goto out;
+		}
+
+		if (kmap_ops) {
+			ret = m2p_add_override(mfn, pages[i], &kmap_ops[i]);
+			if (ret)
+				goto out;
+		}
 	}
 
 out:
 	if (lazy)
 		arch_leave_lazy_mmu_mode();
+
 	return ret;
 }
-EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
+EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
 
-int m2p_remove_override(struct page *page,
-			struct gnttab_map_grant_ref *kmap_op,
-			unsigned long mfn)
+static struct page *m2p_find_override(unsigned long mfn)
+{
+	unsigned long flags;
+	struct list_head *bucket;
+	struct page *p, *ret;
+
+	if (unlikely(!m2p_overrides))
+		return NULL;
+
+	ret = NULL;
+	bucket = &m2p_overrides[mfn_hash(mfn)];
+
+	spin_lock_irqsave(&m2p_override_lock, flags);
+
+	list_for_each_entry(p, bucket, lru) {
+		if (page_private(p) == mfn) {
+			ret = p;
+			break;
+		}
+	}
+
+	spin_unlock_irqrestore(&m2p_override_lock, flags);
+
+	return ret;
+}
+
+static int m2p_remove_override(struct page *page,
+			       struct gnttab_map_grant_ref *kmap_op,
+			       unsigned long mfn)
 {
 	unsigned long flags;
 	unsigned long pfn;
@@ -1072,7 +832,7 @@ int m2p_remove_override(struct page *page,
 		ptep = lookup_address(address, &level);
 
 		if (WARN(ptep == NULL || level != PG_LEVEL_4K,
-					"m2p_remove_override: pfn %lx not mapped", pfn))
+			 "m2p_remove_override: pfn %lx not mapped", pfn))
 			return -EINVAL;
 	}
 
@@ -1102,9 +862,8 @@ int m2p_remove_override(struct page *page,
 			 * hypercall actually returned an error.
 			 */
 			if (kmap_op->handle == GNTST_general_error) {
-				printk(KERN_WARNING "m2p_remove_override: "
-						"pfn %lx mfn %lx, failed to modify kernel mappings",
-						pfn, mfn);
+				pr_warn("m2p_remove_override: pfn %lx mfn %lx, failed to modify kernel mappings",
+					pfn, mfn);
 				put_balloon_scratch_page();
 				return -1;
 			}
@@ -1112,14 +871,14 @@ int m2p_remove_override(struct page *page,
 			xen_mc_batch();
 
 			mcs = __xen_mc_entry(
-					sizeof(struct gnttab_unmap_and_replace));
+				sizeof(struct gnttab_unmap_and_replace));
 			unmap_op = mcs.args;
 			unmap_op->host_addr = kmap_op->host_addr;
 			unmap_op->new_addr = scratch_page_address;
 			unmap_op->handle = kmap_op->handle;
 
 			MULTI_grant_table_op(mcs.mc,
-					GNTTABOP_unmap_and_replace, unmap_op, 1);
+				GNTTABOP_unmap_and_replace, unmap_op, 1);
 
 			mcs = __xen_mc_entry(0);
 			MULTI_update_va_mapping(mcs.mc, scratch_page_address,
@@ -1145,35 +904,56 @@ int m2p_remove_override(struct page *page,
 	 * pfn again. */
 	mfn &= ~FOREIGN_FRAME_BIT;
 	pfn = mfn_to_pfn_no_overrides(mfn);
-	if (get_phys_to_machine(pfn) == FOREIGN_FRAME(mfn) &&
+	if (__pfn_to_mfn(pfn) == FOREIGN_FRAME(mfn) &&
 			m2p_find_override(mfn) == NULL)
 		set_phys_to_machine(pfn, mfn);
 
 	return 0;
 }
-EXPORT_SYMBOL_GPL(m2p_remove_override);
 
-struct page *m2p_find_override(unsigned long mfn)
+int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
+			      struct gnttab_map_grant_ref *kmap_ops,
+			      struct page **pages, unsigned int count)
 {
-	unsigned long flags;
-	struct list_head *bucket = &m2p_overrides[mfn_hash(mfn)];
-	struct page *p, *ret;
+	int i, ret = 0;
+	bool lazy = false;
 
-	ret = NULL;
+	if (xen_feature(XENFEAT_auto_translated_physmap))
+		return 0;
 
-	spin_lock_irqsave(&m2p_override_lock, flags);
+	if (kmap_ops &&
+	    !in_interrupt() &&
+	    paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
+		arch_enter_lazy_mmu_mode();
+		lazy = true;
+	}
 
-	list_for_each_entry(p, bucket, lru) {
-		if (page_private(p) == mfn) {
-			ret = p;
-			break;
+	for (i = 0; i < count; i++) {
+		unsigned long mfn = __pfn_to_mfn(page_to_pfn(pages[i]));
+		unsigned long pfn = page_to_pfn(pages[i]);
+
+		if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
+			ret = -EINVAL;
+			goto out;
 		}
-	}
 
-	spin_unlock_irqrestore(&m2p_override_lock, flags);
+		set_page_private(pages[i], INVALID_P2M_ENTRY);
+		WARN_ON(!PagePrivate(pages[i]));
+		ClearPagePrivate(pages[i]);
+		set_phys_to_machine(pfn, pages[i]->index);
+
+		if (kmap_ops)
+			ret = m2p_remove_override(pages[i], &kmap_ops[i], mfn);
+		if (ret)
+			goto out;
+	}
 
+out:
+	if (lazy)
+		arch_leave_lazy_mmu_mode();
 	return ret;
 }
+EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
 
 unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn)
 {
@@ -1192,79 +972,29 @@ EXPORT_SYMBOL_GPL(m2p_find_override_pfn);
 #include "debugfs.h"
 static int p2m_dump_show(struct seq_file *m, void *v)
 {
-	static const char * const level_name[] = { "top", "middle",
-						"entry", "abnormal", "error"};
-#define TYPE_IDENTITY 0
-#define TYPE_MISSING 1
-#define TYPE_PFN 2
-#define TYPE_UNKNOWN 3
 	static const char * const type_name[] = {
-				[TYPE_IDENTITY] = "identity",
-				[TYPE_MISSING] = "missing",
-				[TYPE_PFN] = "pfn",
-				[TYPE_UNKNOWN] = "abnormal"};
-	unsigned long pfn, prev_pfn_type = 0, prev_pfn_level = 0;
-	unsigned int uninitialized_var(prev_level);
-	unsigned int uninitialized_var(prev_type);
-
-	if (!p2m_top)
-		return 0;
-
-	for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn++) {
-		unsigned topidx = p2m_top_index(pfn);
-		unsigned mididx = p2m_mid_index(pfn);
-		unsigned idx = p2m_index(pfn);
-		unsigned lvl, type;
-
-		lvl = 4;
-		type = TYPE_UNKNOWN;
-		if (p2m_top[topidx] == p2m_mid_missing) {
-			lvl = 0; type = TYPE_MISSING;
-		} else if (p2m_top[topidx] == NULL) {
-			lvl = 0; type = TYPE_UNKNOWN;
-		} else if (p2m_top[topidx][mididx] == NULL) {
-			lvl = 1; type = TYPE_UNKNOWN;
-		} else if (p2m_top[topidx][mididx] == p2m_identity) {
-			lvl = 1; type = TYPE_IDENTITY;
-		} else if (p2m_top[topidx][mididx] == p2m_missing) {
-			lvl = 1; type = TYPE_MISSING;
-		} else if (p2m_top[topidx][mididx][idx] == 0) {
-			lvl = 2; type = TYPE_UNKNOWN;
-		} else if (p2m_top[topidx][mididx][idx] == IDENTITY_FRAME(pfn)) {
-			lvl = 2; type = TYPE_IDENTITY;
-		} else if (p2m_top[topidx][mididx][idx] == INVALID_P2M_ENTRY) {
-			lvl = 2; type = TYPE_MISSING;
-		} else if (p2m_top[topidx][mididx][idx] == pfn) {
-			lvl = 2; type = TYPE_PFN;
-		} else if (p2m_top[topidx][mididx][idx] != pfn) {
-			lvl = 2; type = TYPE_PFN;
-		}
-		if (pfn == 0) {
-			prev_level = lvl;
-			prev_type = type;
-		}
-		if (pfn == MAX_DOMAIN_PAGES-1) {
-			lvl = 3;
-			type = TYPE_UNKNOWN;
-		}
-		if (prev_type != type) {
-			seq_printf(m, " [0x%lx->0x%lx] %s\n",
-				prev_pfn_type, pfn, type_name[prev_type]);
-			prev_pfn_type = pfn;
+				[P2M_TYPE_IDENTITY] = "identity",
+				[P2M_TYPE_MISSING] = "missing",
+				[P2M_TYPE_PFN] = "pfn",
+				[P2M_TYPE_UNKNOWN] = "abnormal"};
+	unsigned long pfn, first_pfn;
+	int type, prev_type;
+
+	prev_type = xen_p2m_elem_type(0);
+	first_pfn = 0;
+
+	for (pfn = 0; pfn < xen_p2m_size; pfn++) {
+		type = xen_p2m_elem_type(pfn);
+		if (type != prev_type) {
+			seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
+				   type_name[prev_type]);
 			prev_type = type;
-		}
-		if (prev_level != lvl) {
-			seq_printf(m, " [0x%lx->0x%lx] level %s\n",
-				prev_pfn_level, pfn, level_name[prev_level]);
-			prev_pfn_level = pfn;
-			prev_level = lvl;
+			first_pfn = pfn;
 		}
 	}
+	seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
+		   type_name[prev_type]);
 	return 0;
-#undef TYPE_IDENTITY
-#undef TYPE_MISSING
-#undef TYPE_PFN
-#undef TYPE_UNKNOWN
 }
 
 static int p2m_dump_open(struct inode *inode, struct file *filp)
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 29834b3fd87f..dfd77dec8e2b 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -30,6 +30,7 @@
 #include "xen-ops.h"
 #include "vdso.h"
 #include "p2m.h"
+#include "mmu.h"
 
 /* These are code, but not functions.  Defined in entry.S */
 extern const char xen_hypervisor_callback[];
@@ -47,8 +48,19 @@ struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS] __initdata;
 /* Number of pages released from the initial allocation. */
 unsigned long xen_released_pages;
 
-/* Buffer used to remap identity mapped pages */
-unsigned long xen_remap_buf[P2M_PER_PAGE] __initdata;
+/*
+ * Buffer used to remap identity mapped pages. We only need the virtual space.
+ * The physical page behind this address is remapped as needed to different
+ * buffer pages.
+ */
+#define REMAP_SIZE	(P2M_PER_PAGE - 3)
+static struct {
+	unsigned long	next_area_mfn;
+	unsigned long	target_pfn;
+	unsigned long	size;
+	unsigned long	mfns[REMAP_SIZE];
+} xen_remap_buf __initdata __aligned(PAGE_SIZE);
+static unsigned long xen_remap_mfn __initdata = INVALID_P2M_ENTRY;
 
 /* 
  * The maximum amount of extra memory compared to the base size.  The
@@ -64,7 +76,6 @@ unsigned long xen_remap_buf[P2M_PER_PAGE] __initdata;
 
 static void __init xen_add_extra_mem(u64 start, u64 size)
 {
-	unsigned long pfn;
 	int i;
 
 	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
@@ -84,75 +95,76 @@ static void __init xen_add_extra_mem(u64 start, u64 size)
 		printk(KERN_WARNING "Warning: not enough extra memory regions\n");
 
 	memblock_reserve(start, size);
+}
 
-	xen_max_p2m_pfn = PFN_DOWN(start + size);
-	for (pfn = PFN_DOWN(start); pfn < xen_max_p2m_pfn; pfn++) {
-		unsigned long mfn = pfn_to_mfn(pfn);
-
-		if (WARN_ONCE(mfn == pfn, "Trying to over-write 1-1 mapping (pfn: %lx)\n", pfn))
-			continue;
-		WARN_ONCE(mfn != INVALID_P2M_ENTRY, "Trying to remove %lx which has %lx mfn!\n",
-			  pfn, mfn);
+static void __init xen_del_extra_mem(u64 start, u64 size)
+{
+	int i;
+	u64 start_r, size_r;
 
-		__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
+	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
+		start_r = xen_extra_mem[i].start;
+		size_r = xen_extra_mem[i].size;
+
+		/* Start of region. */
+		if (start_r == start) {
+			BUG_ON(size > size_r);
+			xen_extra_mem[i].start += size;
+			xen_extra_mem[i].size -= size;
+			break;
+		}
+		/* End of region. */
+		if (start_r + size_r == start + size) {
+			BUG_ON(size > size_r);
+			xen_extra_mem[i].size -= size;
+			break;
+		}
+		/* Mid of region. */
+		if (start > start_r && start < start_r + size_r) {
+			BUG_ON(start + size > start_r + size_r);
+			xen_extra_mem[i].size = start - start_r;
+			/* Calling memblock_reserve() again is okay. */
+			xen_add_extra_mem(start + size, start_r + size_r -
+					  (start + size));
+			break;
+		}
 	}
+	memblock_free(start, size);
 }
 
-static unsigned long __init xen_do_chunk(unsigned long start,
-					 unsigned long end, bool release)
+/*
+ * Called during boot before the p2m list can take entries beyond the
+ * hypervisor supplied p2m list. Entries in extra mem are to be regarded as
+ * invalid.
+ */
+unsigned long __ref xen_chk_extra_mem(unsigned long pfn)
 {
-	struct xen_memory_reservation reservation = {
-		.address_bits = 0,
-		.extent_order = 0,
-		.domid        = DOMID_SELF
-	};
-	unsigned long len = 0;
-	unsigned long pfn;
-	int ret;
+	int i;
+	unsigned long addr = PFN_PHYS(pfn);
 
-	for (pfn = start; pfn < end; pfn++) {
-		unsigned long frame;
-		unsigned long mfn = pfn_to_mfn(pfn);
+	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
+		if (addr >= xen_extra_mem[i].start &&
+		    addr < xen_extra_mem[i].start + xen_extra_mem[i].size)
+			return INVALID_P2M_ENTRY;
+	}
 
-		if (release) {
-			/* Make sure pfn exists to start with */
-			if (mfn == INVALID_P2M_ENTRY || mfn_to_pfn(mfn) != pfn)
-				continue;
-			frame = mfn;
-		} else {
-			if (mfn != INVALID_P2M_ENTRY)
-				continue;
-			frame = pfn;
-		}
-		set_xen_guest_handle(reservation.extent_start, &frame);
-		reservation.nr_extents = 1;
+	return IDENTITY_FRAME(pfn);
+}
 
-		ret = HYPERVISOR_memory_op(release ? XENMEM_decrease_reservation : XENMEM_populate_physmap,
-					   &reservation);
-		WARN(ret != 1, "Failed to %s pfn %lx err=%d\n",
-		     release ? "release" : "populate", pfn, ret);
+/*
+ * Mark all pfns of extra mem as invalid in p2m list.
+ */
+void __init xen_inv_extra_mem(void)
+{
+	unsigned long pfn, pfn_s, pfn_e;
+	int i;
 
-		if (ret == 1) {
-			if (!early_set_phys_to_machine(pfn, release ? INVALID_P2M_ENTRY : frame)) {
-				if (release)
-					break;
-				set_xen_guest_handle(reservation.extent_start, &frame);
-				reservation.nr_extents = 1;
-				ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
-							   &reservation);
-				break;
-			}
-			len++;
-		} else
-			break;
+	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
+		pfn_s = PFN_DOWN(xen_extra_mem[i].start);
+		pfn_e = PFN_UP(xen_extra_mem[i].start + xen_extra_mem[i].size);
+		for (pfn = pfn_s; pfn < pfn_e; pfn++)
+			set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 	}
-	if (len)
-		printk(KERN_INFO "%s %lx-%lx pfn range: %lu pages %s\n",
-		       release ? "Freeing" : "Populating",
-		       start, end, len,
-		       release ? "freed" : "added");
-
-	return len;
 }
 
 /*
@@ -198,26 +210,62 @@ static unsigned long __init xen_find_pfn_range(
 	return done;
 }
 
+static int __init xen_free_mfn(unsigned long mfn)
+{
+	struct xen_memory_reservation reservation = {
+		.address_bits = 0,
+		.extent_order = 0,
+		.domid        = DOMID_SELF
+	};
+
+	set_xen_guest_handle(reservation.extent_start, &mfn);
+	reservation.nr_extents = 1;
+
+	return HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
+}
+
 /*
- * This releases a chunk of memory and then does the identity map. It's used as
+ * This releases a chunk of memory and then does the identity map. It's used
  * as a fallback if the remapping fails.
  */
 static void __init xen_set_identity_and_release_chunk(unsigned long start_pfn,
 	unsigned long end_pfn, unsigned long nr_pages, unsigned long *identity,
 	unsigned long *released)
 {
+	unsigned long len = 0;
+	unsigned long pfn, end;
+	int ret;
+
 	WARN_ON(start_pfn > end_pfn);
 
+	end = min(end_pfn, nr_pages);
+	for (pfn = start_pfn; pfn < end; pfn++) {
+		unsigned long mfn = pfn_to_mfn(pfn);
+
+		/* Make sure pfn exists to start with */
+		if (mfn == INVALID_P2M_ENTRY || mfn_to_pfn(mfn) != pfn)
+			continue;
+
+		ret = xen_free_mfn(mfn);
+		WARN(ret != 1, "Failed to release pfn %lx err=%d\n", pfn, ret);
+
+		if (ret == 1) {
+			if (!__set_phys_to_machine(pfn, INVALID_P2M_ENTRY))
+				break;
+			len++;
+		} else
+			break;
+	}
+
 	/* Need to release pages first */
-	*released += xen_do_chunk(start_pfn, min(end_pfn, nr_pages), true);
+	*released += len;
 	*identity += set_phys_range_identity(start_pfn, end_pfn);
 }
 
 /*
- * Helper function to update both the p2m and m2p tables.
+ * Helper function to update the p2m and m2p tables and kernel mapping.
  */
-static unsigned long __init xen_update_mem_tables(unsigned long pfn,
-						  unsigned long mfn)
+static void __init xen_update_mem_tables(unsigned long pfn, unsigned long mfn)
 {
 	struct mmu_update update = {
 		.ptr = ((unsigned long long)mfn << PAGE_SHIFT) | MMU_MACHPHYS_UPDATE,
@@ -225,161 +273,88 @@ static unsigned long __init xen_update_mem_tables(unsigned long pfn,
 	};
 
 	/* Update p2m */
-	if (!early_set_phys_to_machine(pfn, mfn)) {
+	if (!set_phys_to_machine(pfn, mfn)) {
 		WARN(1, "Failed to set p2m mapping for pfn=%ld mfn=%ld\n",
 		     pfn, mfn);
-		return false;
+		BUG();
 	}
 
 	/* Update m2p */
 	if (HYPERVISOR_mmu_update(&update, 1, NULL, DOMID_SELF) < 0) {
 		WARN(1, "Failed to set m2p mapping for mfn=%ld pfn=%ld\n",
 		     mfn, pfn);
-		return false;
+		BUG();
 	}
 
-	return true;
+	/* Update kernel mapping, but not for highmem. */
+	if ((pfn << PAGE_SHIFT) >= __pa(high_memory))
+		return;
+
+	if (HYPERVISOR_update_va_mapping((unsigned long)__va(pfn << PAGE_SHIFT),
+					 mfn_pte(mfn, PAGE_KERNEL), 0)) {
+		WARN(1, "Failed to update kernel mapping for mfn=%ld pfn=%ld\n",
+		      mfn, pfn);
+		BUG();
+	}
 }
 
 /*
  * This function updates the p2m and m2p tables with an identity map from
- * start_pfn to start_pfn+size and remaps the underlying RAM of the original
- * allocation at remap_pfn. It must do so carefully in P2M_PER_PAGE sized blocks
- * to not exhaust the reserved brk space. Doing it in properly aligned blocks
- * ensures we only allocate the minimum required leaf pages in the p2m table. It
- * copies the existing mfns from the p2m table under the 1:1 map, overwrites
- * them with the identity map and then updates the p2m and m2p tables with the
- * remapped memory.
+ * start_pfn to start_pfn+size and prepares remapping the underlying RAM of the
+ * original allocation at remap_pfn. The information needed for remapping is
+ * saved in the memory itself to avoid the need for allocating buffers. The
+ * complete remap information is contained in a list of MFNs each containing
+ * up to REMAP_SIZE MFNs and the start target PFN for doing the remap.
+ * This enables us to preserve the original mfn sequence while doing the
+ * remapping at a time when the memory management is capable of allocating
+ * virtual and physical memory in arbitrary amounts, see 'xen_remap_memory' and
+ * its callers.
  */
-static unsigned long __init xen_do_set_identity_and_remap_chunk(
+static void __init xen_do_set_identity_and_remap_chunk(
         unsigned long start_pfn, unsigned long size, unsigned long remap_pfn)
 {
+	unsigned long buf = (unsigned long)&xen_remap_buf;
+	unsigned long mfn_save, mfn;
 	unsigned long ident_pfn_iter, remap_pfn_iter;
-	unsigned long ident_start_pfn_align, remap_start_pfn_align;
-	unsigned long ident_end_pfn_align, remap_end_pfn_align;
-	unsigned long ident_boundary_pfn, remap_boundary_pfn;
-	unsigned long ident_cnt = 0;
-	unsigned long remap_cnt = 0;
+	unsigned long ident_end_pfn = start_pfn + size;
 	unsigned long left = size;
-	unsigned long mod;
-	int i;
+	unsigned long ident_cnt = 0;
+	unsigned int i, chunk;
 
 	WARN_ON(size == 0);
 
 	BUG_ON(xen_feature(XENFEAT_auto_translated_physmap));
 
-	/*
-	 * Determine the proper alignment to remap memory in P2M_PER_PAGE sized
-	 * blocks. We need to keep track of both the existing pfn mapping and
-	 * the new pfn remapping.
-	 */
-	mod = start_pfn % P2M_PER_PAGE;
-	ident_start_pfn_align =
-		mod ? (start_pfn - mod + P2M_PER_PAGE) : start_pfn;
-	mod = remap_pfn % P2M_PER_PAGE;
-	remap_start_pfn_align =
-		mod ? (remap_pfn - mod + P2M_PER_PAGE) : remap_pfn;
-	mod = (start_pfn + size) % P2M_PER_PAGE;
-	ident_end_pfn_align = start_pfn + size - mod;
-	mod = (remap_pfn + size) % P2M_PER_PAGE;
-	remap_end_pfn_align = remap_pfn + size - mod;
-
-	/* Iterate over each p2m leaf node in each range */
-	for (ident_pfn_iter = ident_start_pfn_align, remap_pfn_iter = remap_start_pfn_align;
-	     ident_pfn_iter < ident_end_pfn_align && remap_pfn_iter < remap_end_pfn_align;
-	     ident_pfn_iter += P2M_PER_PAGE, remap_pfn_iter += P2M_PER_PAGE) {
-		/* Check we aren't past the end */
-		BUG_ON(ident_pfn_iter + P2M_PER_PAGE > start_pfn + size);
-		BUG_ON(remap_pfn_iter + P2M_PER_PAGE > remap_pfn + size);
-
-		/* Save p2m mappings */
-		for (i = 0; i < P2M_PER_PAGE; i++)
-			xen_remap_buf[i] = pfn_to_mfn(ident_pfn_iter + i);
-
-		/* Set identity map which will free a p2m leaf */
-		ident_cnt += set_phys_range_identity(ident_pfn_iter,
-			ident_pfn_iter + P2M_PER_PAGE);
+	mfn_save = virt_to_mfn(buf);
 
-#ifdef DEBUG
-		/* Helps verify a p2m leaf has been freed */
-		for (i = 0; i < P2M_PER_PAGE; i++) {
-			unsigned int pfn = ident_pfn_iter + i;
-			BUG_ON(pfn_to_mfn(pfn) != pfn);
-		}
-#endif
-		/* Now remap memory */
-		for (i = 0; i < P2M_PER_PAGE; i++) {
-			unsigned long mfn = xen_remap_buf[i];
-
-			/* This will use the p2m leaf freed above */
-			if (!xen_update_mem_tables(remap_pfn_iter + i, mfn)) {
-				WARN(1, "Failed to update mem mapping for pfn=%ld mfn=%ld\n",
-					remap_pfn_iter + i, mfn);
-				return 0;
-			}
-
-			remap_cnt++;
-		}
-
-		left -= P2M_PER_PAGE;
-	}
-
-	/* Max boundary space possible */
-	BUG_ON(left > (P2M_PER_PAGE - 1) * 2);
+	for (ident_pfn_iter = start_pfn, remap_pfn_iter = remap_pfn;
+	     ident_pfn_iter < ident_end_pfn;
+	     ident_pfn_iter += REMAP_SIZE, remap_pfn_iter += REMAP_SIZE) {
+		chunk = (left < REMAP_SIZE) ? left : REMAP_SIZE;
 
-	/* Now handle the boundary conditions */
-	ident_boundary_pfn = start_pfn;
-	remap_boundary_pfn = remap_pfn;
-	for (i = 0; i < left; i++) {
-		unsigned long mfn;
+		/* Map first pfn to xen_remap_buf */
+		mfn = pfn_to_mfn(ident_pfn_iter);
+		set_pte_mfn(buf, mfn, PAGE_KERNEL);
 
-		/* These two checks move from the start to end boundaries */
-		if (ident_boundary_pfn == ident_start_pfn_align)
-			ident_boundary_pfn = ident_pfn_iter;
-		if (remap_boundary_pfn == remap_start_pfn_align)
-			remap_boundary_pfn = remap_pfn_iter;
+		/* Save mapping information in page */
+		xen_remap_buf.next_area_mfn = xen_remap_mfn;
+		xen_remap_buf.target_pfn = remap_pfn_iter;
+		xen_remap_buf.size = chunk;
+		for (i = 0; i < chunk; i++)
+			xen_remap_buf.mfns[i] = pfn_to_mfn(ident_pfn_iter + i);
 
-		/* Check we aren't past the end */
-		BUG_ON(ident_boundary_pfn >= start_pfn + size);
-		BUG_ON(remap_boundary_pfn >= remap_pfn + size);
-
-		mfn = pfn_to_mfn(ident_boundary_pfn);
-
-		if (!xen_update_mem_tables(remap_boundary_pfn, mfn)) {
-			WARN(1, "Failed to update mem mapping for pfn=%ld mfn=%ld\n",
-				remap_pfn_iter + i, mfn);
-			return 0;
-		}
-		remap_cnt++;
+		/* Put remap buf into list. */
+		xen_remap_mfn = mfn;
 
-		ident_boundary_pfn++;
-		remap_boundary_pfn++;
-	}
+		/* Set identity map */
+		ident_cnt += set_phys_range_identity(ident_pfn_iter,
+			ident_pfn_iter + chunk);
 
-	/* Finish up the identity map */
-	if (ident_start_pfn_align >= ident_end_pfn_align) {
-		/*
-                 * In this case we have an identity range which does not span an
-                 * aligned block so everything needs to be identity mapped here.
-                 * If we didn't check this we might remap too many pages since
-                 * the align boundaries are not meaningful in this case.
-	         */
-		ident_cnt += set_phys_range_identity(start_pfn,
-			start_pfn + size);
-	} else {
-		/* Remapped above so check each end of the chunk */
-		if (start_pfn < ident_start_pfn_align)
-			ident_cnt += set_phys_range_identity(start_pfn,
-				ident_start_pfn_align);
-		if (start_pfn + size > ident_pfn_iter)
-			ident_cnt += set_phys_range_identity(ident_pfn_iter,
-				start_pfn + size);
+		left -= chunk;
 	}
 
-	BUG_ON(ident_cnt != size);
-	BUG_ON(remap_cnt != size);
-
-	return size;
+	/* Restore old xen_remap_buf mapping */
+	set_pte_mfn(buf, mfn_save, PAGE_KERNEL);
 }
 
 /*
@@ -396,8 +371,7 @@ static unsigned long __init xen_do_set_identity_and_remap_chunk(
 static unsigned long __init xen_set_identity_and_remap_chunk(
         const struct e820entry *list, size_t map_size, unsigned long start_pfn,
 	unsigned long end_pfn, unsigned long nr_pages, unsigned long remap_pfn,
-	unsigned long *identity, unsigned long *remapped,
-	unsigned long *released)
+	unsigned long *identity, unsigned long *released)
 {
 	unsigned long pfn;
 	unsigned long i = 0;
@@ -431,19 +405,12 @@ static unsigned long __init xen_set_identity_and_remap_chunk(
 		if (size > remap_range_size)
 			size = remap_range_size;
 
-		if (!xen_do_set_identity_and_remap_chunk(cur_pfn, size, remap_pfn)) {
-			WARN(1, "Failed to remap 1:1 memory cur_pfn=%ld size=%ld remap_pfn=%ld\n",
-				cur_pfn, size, remap_pfn);
-			xen_set_identity_and_release_chunk(cur_pfn,
-				cur_pfn + left, nr_pages, identity, released);
-			break;
-		}
+		xen_do_set_identity_and_remap_chunk(cur_pfn, size, remap_pfn);
 
 		/* Update variables to reflect new mappings. */
 		i += size;
 		remap_pfn += size;
 		*identity += size;
-		*remapped += size;
 	}
 
 	/*
@@ -458,13 +425,12 @@ static unsigned long __init xen_set_identity_and_remap_chunk(
 	return remap_pfn;
 }
 
-static unsigned long __init xen_set_identity_and_remap(
+static void __init xen_set_identity_and_remap(
 	const struct e820entry *list, size_t map_size, unsigned long nr_pages,
 	unsigned long *released)
 {
 	phys_addr_t start = 0;
 	unsigned long identity = 0;
-	unsigned long remapped = 0;
 	unsigned long last_pfn = nr_pages;
 	const struct e820entry *entry;
 	unsigned long num_released = 0;
@@ -494,8 +460,7 @@ static unsigned long __init xen_set_identity_and_remap(
 				last_pfn = xen_set_identity_and_remap_chunk(
 						list, map_size, start_pfn,
 						end_pfn, nr_pages, last_pfn,
-						&identity, &remapped,
-						&num_released);
+						&identity, &num_released);
 			start = end;
 		}
 	}
@@ -503,12 +468,63 @@ static unsigned long __init xen_set_identity_and_remap(
 	*released = num_released;
 
 	pr_info("Set %ld page(s) to 1-1 mapping\n", identity);
-	pr_info("Remapped %ld page(s), last_pfn=%ld\n", remapped,
-		last_pfn);
 	pr_info("Released %ld page(s)\n", num_released);
+}
+
+/*
+ * Remap the memory prepared in xen_do_set_identity_and_remap_chunk().
+ * The remap information (which mfn remap to which pfn) is contained in the
+ * to be remapped memory itself in a linked list anchored at xen_remap_mfn.
+ * This scheme allows to remap the different chunks in arbitrary order while
+ * the resulting mapping will be independant from the order.
+ */
+void __init xen_remap_memory(void)
+{
+	unsigned long buf = (unsigned long)&xen_remap_buf;
+	unsigned long mfn_save, mfn, pfn;
+	unsigned long remapped = 0;
+	unsigned int i;
+	unsigned long pfn_s = ~0UL;
+	unsigned long len = 0;
+
+	mfn_save = virt_to_mfn(buf);
+
+	while (xen_remap_mfn != INVALID_P2M_ENTRY) {
+		/* Map the remap information */
+		set_pte_mfn(buf, xen_remap_mfn, PAGE_KERNEL);
 
-	return last_pfn;
+		BUG_ON(xen_remap_mfn != xen_remap_buf.mfns[0]);
+
+		pfn = xen_remap_buf.target_pfn;
+		for (i = 0; i < xen_remap_buf.size; i++) {
+			mfn = xen_remap_buf.mfns[i];
+			xen_update_mem_tables(pfn, mfn);
+			remapped++;
+			pfn++;
+		}
+		if (pfn_s == ~0UL || pfn == pfn_s) {
+			pfn_s = xen_remap_buf.target_pfn;
+			len += xen_remap_buf.size;
+		} else if (pfn_s + len == xen_remap_buf.target_pfn) {
+			len += xen_remap_buf.size;
+		} else {
+			xen_del_extra_mem(PFN_PHYS(pfn_s), PFN_PHYS(len));
+			pfn_s = xen_remap_buf.target_pfn;
+			len = xen_remap_buf.size;
+		}
+
+		mfn = xen_remap_mfn;
+		xen_remap_mfn = xen_remap_buf.next_area_mfn;
+	}
+
+	if (pfn_s != ~0UL && len)
+		xen_del_extra_mem(PFN_PHYS(pfn_s), PFN_PHYS(len));
+
+	set_pte_mfn(buf, mfn_save, PAGE_KERNEL);
+
+	pr_info("Remapped %ld page(s)\n", remapped);
 }
+
 static unsigned long __init xen_get_max_pages(void)
 {
 	unsigned long max_pages = MAX_DOMAIN_PAGES;
@@ -569,7 +585,6 @@ char * __init xen_memory_setup(void)
 	int rc;
 	struct xen_memory_map memmap;
 	unsigned long max_pages;
-	unsigned long last_pfn = 0;
 	unsigned long extra_pages = 0;
 	int i;
 	int op;
@@ -616,17 +631,14 @@ char * __init xen_memory_setup(void)
 		extra_pages += max_pages - max_pfn;
 
 	/*
-	 * Set identity map on non-RAM pages and remap the underlying RAM.
+	 * Set identity map on non-RAM pages and prepare remapping the
+	 * underlying RAM.
 	 */
-	last_pfn = xen_set_identity_and_remap(map, memmap.nr_entries, max_pfn,
-					      &xen_released_pages);
+	xen_set_identity_and_remap(map, memmap.nr_entries, max_pfn,
+				   &xen_released_pages);
 
 	extra_pages += xen_released_pages;
 
-	if (last_pfn > max_pfn) {
-		max_pfn = min(MAX_DOMAIN_PAGES, last_pfn);
-		mem_end = PFN_PHYS(max_pfn);
-	}
 	/*
 	 * Clamp the amount of extra memory to a EXTRA_MEM_RATIO
 	 * factor the base size.  On non-highmem systems, the base
@@ -653,6 +665,7 @@ char * __init xen_memory_setup(void)
 				size = min(size, (u64)extra_pages * PAGE_SIZE);
 				extra_pages -= size / PAGE_SIZE;
 				xen_add_extra_mem(addr, size);
+				xen_max_p2m_pfn = PFN_DOWN(addr + size);
 			} else
 				type = E820_UNUSABLE;
 		}
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 4ab9298c5e17..5686bd9d58cc 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -29,11 +29,13 @@ void xen_build_mfn_list_list(void);
 void xen_setup_machphys_mapping(void);
 void xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn);
 void xen_reserve_top(void);
-extern unsigned long xen_max_p2m_pfn;
 
 void xen_mm_pin_all(void);
 void xen_mm_unpin_all(void);
 
+unsigned long __ref xen_chk_extra_mem(unsigned long pfn);
+void __init xen_inv_extra_mem(void);
+void __init xen_remap_memory(void);
 char * __init xen_memory_setup(void);
 char * xen_auto_xlated_memory_setup(void);
 void __init xen_arch_setup(void);
@@ -46,7 +48,7 @@ void xen_hvm_init_shared_info(void);
 void xen_unplug_emulated_devices(void);
 
 void __init xen_build_dynamic_phys_to_machine(void);
-unsigned long __init xen_revector_p2m_tree(void);
+void __init xen_vmalloc_p2m_tree(void);
 
 void xen_init_irq_ops(void);
 void xen_setup_timer(int cpu);