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[PATCH v2 5/6] xen: modify page table construction


From: Juergen Gross
Subject: [PATCH v2 5/6] xen: modify page table construction
Date: Thu, 11 Feb 2016 08:53:25 +0100

Modify the page table construction to allow multiple virtual regions
to be mapped. This is done as preparation for removing the p2m list
from the initial kernel mapping in order to support huge pv domains.

This allows a cleaner approach for mapping the relocator page by
using this capability.

The interface to the assembler level of the relocator has to be changed
in order to be able to process multiple page table areas.

Signed-off-by: Juergen Gross <address@hidden>
---
 grub-core/lib/i386/xen/relocator.S   |  47 +++---
 grub-core/lib/x86_64/xen/relocator.S |  44 +++--
 grub-core/lib/xen/relocator.c        |  22 ++-
 grub-core/loader/i386/xen.c          | 313 +++++++++++++++++++++++------------
 include/grub/xen/relocator.h         |   6 +-
 5 files changed, 277 insertions(+), 155 deletions(-)

diff --git a/grub-core/lib/i386/xen/relocator.S 
b/grub-core/lib/i386/xen/relocator.S
index 694a54c..c23b405 100644
--- a/grub-core/lib/i386/xen/relocator.S
+++ b/grub-core/lib/i386/xen/relocator.S
@@ -50,41 +50,45 @@ VARIABLE(grub_relocator_xen_remapper_map_high)
        jmp *%ebx
 
 LOCAL(cont):
-       xorl    %eax, %eax
-       movl    %eax, %ebp
+       /* mov imm32, %eax */
+       .byte   0xb8
+VARIABLE(grub_relocator_xen_paging_areas_addr)
+       .long   0
+       movl    %eax, %ebx
 1:
-
+       movl    0(%ebx), %ebp
+       movl    4(%ebx), %ecx
+       testl   %ecx, %ecx
+       jz      3f
+       addl    $8, %ebx
+       movl    %ebx, %esp
+
+2:
+       movl    %ecx, %edi
        /* mov imm32, %eax */
        .byte   0xb8
 VARIABLE(grub_relocator_xen_mfn_list)
        .long   0
-       movl    %eax, %edi
-       movl    %ebp, %eax
-       movl    0(%edi, %eax, 4), %ecx
-
-       /* mov imm32, %ebx */
-       .byte   0xbb
-VARIABLE(grub_relocator_xen_paging_start)
-       .long   0
-       shll    $12, %eax
-       addl    %eax, %ebx
+       movl    0(%eax, %ebp, 4), %ecx
+       movl    %ebp, %ebx
+       shll    $12, %ebx
        movl    %ecx, %edx
        shll    $12,  %ecx
        shrl    $20,  %edx
        orl     $5, %ecx
        movl    $2, %esi
        movl    $__HYPERVISOR_update_va_mapping, %eax
-       int     $0x82
+       int     $0x82   /* parameters: eax, ebx, ecx, edx, esi */
 
        incl    %ebp
-       /* mov imm32, %ecx */
-       .byte   0xb9
-VARIABLE(grub_relocator_xen_paging_size)
-       .long   0
-       cmpl    %ebp, %ecx
+       movl    %edi, %ecx
+
+       loop    2b
 
-       ja      1b
+       mov     %esp, %ebx
+       jmp     1b
 
+3:
        /* mov imm32, %ebx */
        .byte   0xbb
 VARIABLE(grub_relocator_xen_mmu_op_addr)
@@ -102,6 +106,9 @@ VARIABLE(grub_relocator_xen_remap_continue)
 
        jmp *%eax
 
+VARIABLE(grub_relocator_xen_paging_areas)
+       .long   0, 0, 0, 0, 0, 0, 0, 0
+
 VARIABLE(grub_relocator_xen_mmu_op)
        .space 256
 
diff --git a/grub-core/lib/x86_64/xen/relocator.S 
b/grub-core/lib/x86_64/xen/relocator.S
index 92e9e72..dbb90c7 100644
--- a/grub-core/lib/x86_64/xen/relocator.S
+++ b/grub-core/lib/x86_64/xen/relocator.S
@@ -50,31 +50,24 @@ VARIABLE(grub_relocator_xen_remapper_map)
 
 LOCAL(cont):
        
-       /* mov imm64, %rcx */
-       .byte   0x48
-       .byte   0xb9
-VARIABLE(grub_relocator_xen_paging_size)
-       .quad   0
-
-       /* mov imm64, %rax */
-       .byte   0x48
-       .byte   0xb8
-VARIABLE(grub_relocator_xen_paging_start)
-       .quad   0
-
-       movq    %rax, %r12
-
        /* mov imm64, %rax */
        .byte   0x48
        .byte   0xb8
 VARIABLE(grub_relocator_xen_mfn_list)
        .quad   0
 
-       movq    %rax, %rsi
+       movq    %rax, %rbx
+       leaq    EXT_C(grub_relocator_xen_paging_areas) (%rip), %r8
+
 1:
+       movq    0(%r8), %r12
+       movq    8(%r8), %rcx
+       testq   %rcx, %rcx
+       jz      3f
+2:
        movq    %r12, %rdi
-       movq    %rsi, %rbx
-       movq    0(%rsi), %rsi
+       shlq    $12, %rdi
+       movq    (%rbx, %r12, 8), %rsi
        shlq    $12,  %rsi
        orq     $5, %rsi
        movq    $2, %rdx
@@ -83,13 +76,15 @@ VARIABLE(grub_relocator_xen_mfn_list)
        syscall
 
        movq    %r9, %rcx
-       addq    $8, %rbx
-       addq    $4096, %r12
-       movq    %rbx, %rsi
+       incq    %r12
+
+       loop 2b
 
-       loop 1b
+       addq    $16, %r8
+       jmp     1b
 
-       leaq   LOCAL(mmu_op) (%rip), %rdi
+3:
+       leaq   EXT_C(grub_relocator_xen_mmu_op) (%rip), %rdi
        movq   $3, %rsi
        movq   $0, %rdx
        movq   $0x7FF0, %r10
@@ -104,7 +99,10 @@ VARIABLE(grub_relocator_xen_remap_continue)
 
        jmp *%rax
 
-LOCAL(mmu_op):
+VARIABLE(grub_relocator_xen_paging_areas)
+       /* array of start, size pairs, size 0 is end marker */
+       .quad   0, 0, 0, 0, 0, 0, 0, 0
+
 VARIABLE(grub_relocator_xen_mmu_op)
        .space 256
 
diff --git a/grub-core/lib/xen/relocator.c b/grub-core/lib/xen/relocator.c
index 8f427d3..bc29055 100644
--- a/grub-core/lib/xen/relocator.c
+++ b/grub-core/lib/xen/relocator.c
@@ -36,15 +36,15 @@ extern grub_uint8_t grub_relocator_xen_remap_end;
 extern grub_xen_reg_t grub_relocator_xen_stack;
 extern grub_xen_reg_t grub_relocator_xen_start_info;
 extern grub_xen_reg_t grub_relocator_xen_entry_point;
-extern grub_xen_reg_t grub_relocator_xen_paging_start;
-extern grub_xen_reg_t grub_relocator_xen_paging_size;
 extern grub_xen_reg_t grub_relocator_xen_remapper_virt;
 extern grub_xen_reg_t grub_relocator_xen_remapper_virt2;
 extern grub_xen_reg_t grub_relocator_xen_remapper_map;
 extern grub_xen_reg_t grub_relocator_xen_mfn_list;
+extern grub_xen_reg_t grub_relocator_xen_paging_areas[2 * XEN_MAX_MAPPINGS];
 extern grub_xen_reg_t grub_relocator_xen_remap_continue;
 #ifdef __i386__
 extern grub_xen_reg_t grub_relocator_xen_mmu_op_addr;
+extern grub_xen_reg_t grub_relocator_xen_paging_areas_addr;
 extern grub_xen_reg_t grub_relocator_xen_remapper_map_high;
 #endif
 extern mmuext_op_t grub_relocator_xen_mmu_op[3];
@@ -61,6 +61,7 @@ grub_relocator_xen_boot (struct grub_relocator *rel,
 {
   grub_err_t err;
   void *relst;
+  int i;
   grub_relocator_chunk_t ch, ch_tramp;
   grub_xen_mfn_t *mfn_list =
     (grub_xen_mfn_t *) grub_xen_start_page_addr->mfn_list;
@@ -77,8 +78,11 @@ grub_relocator_xen_boot (struct grub_relocator *rel,
   grub_relocator_xen_stack = state.stack;
   grub_relocator_xen_start_info = state.start_info;
   grub_relocator_xen_entry_point = state.entry_point;
-  grub_relocator_xen_paging_start = state.paging_start << 12;
-  grub_relocator_xen_paging_size = state.paging_size;
+  for (i = 0; i < XEN_MAX_MAPPINGS; i++)
+    {
+      grub_relocator_xen_paging_areas[2 * i] = state.paging_start[i];
+      grub_relocator_xen_paging_areas[2 * i + 1] = state.paging_size[i];
+    }
   grub_relocator_xen_remapper_virt = remapper_virt;
   grub_relocator_xen_remapper_virt2 = remapper_virt;
   grub_relocator_xen_remap_continue = trampoline_virt;
@@ -88,10 +92,12 @@ grub_relocator_xen_boot (struct grub_relocator *rel,
   grub_relocator_xen_remapper_map_high = (mfn_list[remapper_pfn] >> 20);
   grub_relocator_xen_mmu_op_addr = (char *) &grub_relocator_xen_mmu_op
     - (char *) &grub_relocator_xen_remap_start + remapper_virt;
+  grub_relocator_xen_paging_areas_addr =
+    (char *) &grub_relocator_xen_paging_areas
+    - (char *) &grub_relocator_xen_remap_start + remapper_virt;
 #endif
 
-  grub_relocator_xen_mfn_list = state.mfn_list
-    + state.paging_start * sizeof (grub_addr_t);
+  grub_relocator_xen_mfn_list = state.mfn_list;
 
   grub_memset (grub_relocator_xen_mmu_op, 0,
               sizeof (grub_relocator_xen_mmu_op));
@@ -100,9 +106,9 @@ grub_relocator_xen_boot (struct grub_relocator *rel,
 #else
   grub_relocator_xen_mmu_op[0].cmd = MMUEXT_PIN_L4_TABLE;
 #endif
-  grub_relocator_xen_mmu_op[0].arg1.mfn = mfn_list[state.paging_start];
+  grub_relocator_xen_mmu_op[0].arg1.mfn = mfn_list[state.paging_start[0]];
   grub_relocator_xen_mmu_op[1].cmd = MMUEXT_NEW_BASEPTR;
-  grub_relocator_xen_mmu_op[1].arg1.mfn = mfn_list[state.paging_start];
+  grub_relocator_xen_mmu_op[1].arg1.mfn = mfn_list[state.paging_start[0]];
   grub_relocator_xen_mmu_op[2].cmd = MMUEXT_UNPIN_TABLE;
   grub_relocator_xen_mmu_op[2].arg1.mfn =
     mfn_list[grub_xen_start_page_addr->pt_base >> 12];
diff --git a/grub-core/loader/i386/xen.c b/grub-core/loader/i386/xen.c
index 0f41048..5e10420 100644
--- a/grub-core/loader/i386/xen.c
+++ b/grub-core/loader/i386/xen.c
@@ -42,6 +42,29 @@
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
+#ifdef __x86_64__
+#define NUMBER_OF_LEVELS 4
+#define INTERMEDIATE_OR 7
+#define VIRT_MASK 0x0000ffffffffffffULL
+#else
+#define NUMBER_OF_LEVELS 3
+#define INTERMEDIATE_OR 3
+#define VIRT_MASK 0x00000000ffffffffULL
+#endif
+
+struct grub_xen_mapping_lvl {
+  grub_uint64_t virt_start;
+  grub_uint64_t virt_end;
+  grub_uint64_t pfn_start;
+  grub_uint64_t n_pt_pages;
+};
+
+struct grub_xen_mapping {
+  grub_uint64_t *where;
+  struct grub_xen_mapping_lvl area;
+  struct grub_xen_mapping_lvl lvls[NUMBER_OF_LEVELS];
+};
+
 static struct grub_relocator *relocator = NULL;
 static grub_uint64_t max_addr;
 static grub_dl_t my_mod;
@@ -56,9 +79,10 @@ static struct grub_relocator_xen_state state;
 static grub_xen_mfn_t *virt_mfn_list;
 static struct start_info *virt_start_info;
 static grub_xen_mfn_t console_pfn;
-static grub_uint64_t *virt_pgtable;
-static grub_uint64_t pgtbl_start;
 static grub_uint64_t pgtbl_end;
+static struct grub_xen_mapping mappings[XEN_MAX_MAPPINGS];
+static int n_mappings;
+static struct grub_xen_mapping *map_reloc;
 
 #define PAGE_SIZE 4096
 #define MAX_MODULES (PAGE_SIZE / sizeof (struct xen_multiboot_mod_list))
@@ -75,100 +99,162 @@ page2offset (grub_uint64_t page)
   return page << PAGE_SHIFT;
 }
 
-#ifdef __x86_64__
-#define NUMBER_OF_LEVELS 4
-#define INTERMEDIATE_OR 7
-#else
-#define NUMBER_OF_LEVELS 3
-#define INTERMEDIATE_OR 3
-#endif
-
-static grub_uint64_t
-get_pgtable_size (grub_uint64_t total_pages, grub_uint64_t virt_base)
+static grub_err_t
+get_pgtable_size (grub_uint64_t from, grub_uint64_t to, grub_uint64_t pfn)
 {
-  if (!virt_base)
-    total_pages++;
-  grub_uint64_t ret = 0;
-  grub_uint64_t ll = total_pages;
-  int i;
-  for (i = 0; i < NUMBER_OF_LEVELS; i++)
-    {
-      ll = (ll + POINTERS_PER_PAGE - 1) >> LOG_POINTERS_PER_PAGE;
-      /* PAE wants all 4 root directories present.  */
-#ifdef __i386__
-      if (i == 1)
-       ll = 4;
-#endif
-      ret += ll;
-    }
-  for (i = 1; i < NUMBER_OF_LEVELS; i++)
-    if (virt_base >> (PAGE_SHIFT + i * LOG_POINTERS_PER_PAGE))
-      ret++;
-  return ret;
-}
+  struct grub_xen_mapping *map, *map_cmp;
+  grub_uint64_t mask, bits;
+  int i, m;
 
-static void
-generate_page_table (grub_uint64_t *where, grub_uint64_t paging_start,
-                    grub_uint64_t paging_end, grub_uint64_t total_pages,
-                    grub_uint64_t virt_base, grub_xen_mfn_t *mfn_list)
-{
-  if (!virt_base)
-    paging_end++;
+  if (n_mappings == XEN_MAX_MAPPINGS)
+    return grub_error (GRUB_ERR_BUG, "too many mapped areas");
+
+  grub_dprintf ("xen", "get_pgtable_size %d from=%llx, to=%llx, pfn=%llx\n",
+               n_mappings, (unsigned long long) from, (unsigned long long) to,
+               (unsigned long long) pfn);
 
-  grub_uint64_t lx[NUMBER_OF_LEVELS], lxs[NUMBER_OF_LEVELS];
-  grub_uint64_t nlx, nls, sz = 0;
-  int l;
+  map = mappings + n_mappings;
+  grub_memset (map, 0, sizeof (*map));
 
-  nlx = paging_end;
-  nls = virt_base >> PAGE_SHIFT;
-  for (l = 0; l < NUMBER_OF_LEVELS; l++)
+  map->area.virt_start = from & VIRT_MASK;
+  map->area.virt_end = (to - 1) & VIRT_MASK;
+  map->area.n_pt_pages = 0;
+
+  for (i = NUMBER_OF_LEVELS - 1; i >= 0; i--)
     {
-      nlx = (nlx + POINTERS_PER_PAGE - 1) >> LOG_POINTERS_PER_PAGE;
-      /* PAE wants all 4 root directories present.  */
+      map->lvls[i].pfn_start = pfn + map->area.n_pt_pages;
+      if (i == NUMBER_OF_LEVELS - 1)
+       {
+         if (n_mappings == 0)
+           {
+             map->lvls[i].virt_start = 0;
+             map->lvls[i].virt_end = VIRT_MASK;
+             map->lvls[i].n_pt_pages = 1;
+             map->area.n_pt_pages++;
+           }
+         continue;
+       }
+
+      bits = PAGE_SHIFT + (i + 1) * LOG_POINTERS_PER_PAGE;
+      mask = (1ULL << bits) - 1;
+      map->lvls[i].virt_start = map->area.virt_start & ~mask;
+      map->lvls[i].virt_end = map->area.virt_end | mask;
 #ifdef __i386__
-      if (l == 1)
-       nlx = 4;
+      /* PAE wants last root directory present. */
+      if (i == 1 && to <= 0xc0000000 && n_mappings == 0)
+       map->lvls[i].virt_end = VIRT_MASK;
 #endif
-      lx[l] = nlx;
-      sz += lx[l];
-      lxs[l] = nls & (POINTERS_PER_PAGE - 1);
-      if (nls && l != 0)
-       sz++;
-      nls >>= LOG_POINTERS_PER_PAGE;
+      for (m = 0; m < n_mappings; m++)
+       {
+         map_cmp = mappings + m;
+         if (map_cmp->lvls[i].virt_start == map_cmp->lvls[i].virt_end)
+           continue;
+         if (map->lvls[i].virt_start >= map_cmp->lvls[i].virt_start &&
+             map->lvls[i].virt_end <= map_cmp->lvls[i].virt_end)
+          {
+            map->lvls[i].virt_start = 0;
+            map->lvls[i].virt_end = 0;
+            break;
+          }
+          if (map->lvls[i].virt_start >= map_cmp->lvls[i].virt_start &&
+              map->lvls[i].virt_start <= map_cmp->lvls[i].virt_end)
+            map->lvls[i].virt_start = map_cmp->lvls[i].virt_end + 1;
+          if (map->lvls[i].virt_end >= map_cmp->lvls[i].virt_start &&
+              map->lvls[i].virt_end <= map_cmp->lvls[i].virt_end)
+            map->lvls[i].virt_end = map_cmp->lvls[i].virt_start - 1;
+       }
+      if (map->lvls[i].virt_start < map->lvls[i].virt_end)
+       map->lvls[i].n_pt_pages =
+         ((map->lvls[i].virt_end - map->lvls[i].virt_start) >> bits) + 1;
+      map->area.n_pt_pages += map->lvls[i].n_pt_pages;
+      grub_dprintf ("xen", "get_pgtable_size level %d: virt %llx-%llx %d 
pts\n",
+                   i, (unsigned long long)  map->lvls[i].virt_start,
+                   (unsigned long long)  map->lvls[i].virt_end,
+                   (int) map->lvls[i].n_pt_pages);
     }
 
-  grub_uint64_t lp;
-  grub_uint64_t j;
-  grub_uint64_t *pg = (grub_uint64_t *) where;
-  int pr = 0;
+  grub_dprintf ("xen", "get_pgtable_size return: %d page tables\n",
+               (int) map->area.n_pt_pages);
+
+  state.paging_start[n_mappings] = pfn;
+  state.paging_size[n_mappings] = map->area.n_pt_pages;
+
+  return GRUB_ERR_NONE;
+}
+
+static grub_uint64_t *
+get_pg_table_virt (int mapping, int level)
+{
+  grub_uint64_t pfn;
+  struct grub_xen_mapping *map;
+
+  map = mappings + mapping;
+  pfn = map->lvls[level].pfn_start - map->lvls[NUMBER_OF_LEVELS - 1].pfn_start;
+  return map->where + pfn * POINTERS_PER_PAGE;
+}
 
-  grub_memset (pg, 0, sz * PAGE_SIZE);
+static grub_uint64_t
+get_pg_table_prot (int level, grub_uint64_t pfn)
+{
+  int m;
+  grub_uint64_t pfn_s, pfn_e;
 
-  lp = paging_start + lx[NUMBER_OF_LEVELS - 1];
-  for (l = NUMBER_OF_LEVELS - 1; l >= 1; l--)
+  if (level > 0)
+    return INTERMEDIATE_OR;
+  for (m = 0; m < n_mappings; m++)
     {
-      if (lxs[l] || pr)
-       pg[0] = page2offset (mfn_list[lp++]) | INTERMEDIATE_OR;
-      if (pr)
-       pg += POINTERS_PER_PAGE;
-      for (j = 0; j < lx[l - 1]; j++)
-       pg[j + lxs[l]] = page2offset (mfn_list[lp++]) | INTERMEDIATE_OR;
-      pg += lx[l] * POINTERS_PER_PAGE;
-      if (lxs[l])
-       pr = 1;
+      pfn_s = mappings[m].lvls[NUMBER_OF_LEVELS - 1].pfn_start;
+      pfn_e = mappings[m].area.n_pt_pages + pfn_s;
+      if (pfn >= pfn_s && pfn < pfn_e)
+       return 5;
     }
+  return 7;
+}
+
+static void
+generate_page_table (grub_xen_mfn_t *mfn_list)
+{
+  int l, m1, m2;
+  long p, p_s, p_e;
+  grub_uint64_t start, end, pfn;
+  grub_uint64_t *pg;
+  struct grub_xen_mapping_lvl *lvl;
 
-  if (lxs[0] || pr)
-    pg[0] = page2offset (mfn_list[total_pages]) | 5;
-  if (pr)
-    pg += POINTERS_PER_PAGE;
+  for (m1 = 0; m1 < n_mappings; m1++)
+    grub_memset (mappings[m1].where, 0,
+                mappings[m1].area.n_pt_pages * PAGE_SIZE);
 
-  for (j = 0; j < paging_end; j++)
+  for (l = NUMBER_OF_LEVELS - 1; l >= 0; l--)
     {
-      if (j >= paging_start && j < lp)
-       pg[j + lxs[0]] = page2offset (mfn_list[j]) | 5;
-      else
-       pg[j + lxs[0]] = page2offset (mfn_list[j]) | 7;
+      for (m1 = 0; m1 < n_mappings; m1++)
+       {
+         start = mappings[m1].lvls[l].virt_start;
+         end = mappings[m1].lvls[l].virt_end;
+         pg = get_pg_table_virt(m1, l);
+         for (m2 = 0; m2 < n_mappings; m2++)
+           {
+             lvl = (l > 0) ? mappings[m2].lvls + l - 1 : &mappings[m2].area;
+             if (l > 0 && lvl->n_pt_pages == 0)
+               continue;
+             if (lvl->virt_start >= end || lvl->virt_end <= start)
+               continue;
+             p_s = (grub_max (start, lvl->virt_start) - start) >>
+                   (PAGE_SHIFT + l * LOG_POINTERS_PER_PAGE);
+             p_e = (grub_min (end, lvl->virt_end) - start) >>
+                   (PAGE_SHIFT + l * LOG_POINTERS_PER_PAGE);
+             pfn = ((grub_max (start, lvl->virt_start) - lvl->virt_start) >>
+                    (PAGE_SHIFT + l * LOG_POINTERS_PER_PAGE)) + lvl->pfn_start;
+             grub_dprintf ("xen", "write page table entries level %d pg %p "
+                           "mapping %d/%d index %lx-%lx pfn %llx\n",
+                           l, pg, m1, m2, p_s, p_e, (unsigned long long) pfn);
+             for (p = p_s; p <= p_e; p++)
+               {
+                 pg[p] = page2offset (mfn_list[pfn]) |
+                         get_pg_table_prot (l, pfn);
+                 pfn++;
+               }
+           }
+       }
     }
 }
 
@@ -269,39 +355,62 @@ grub_xen_pt_alloc (void)
   grub_relocator_chunk_t ch;
   grub_err_t err;
   grub_uint64_t nr_info_pages;
-  grub_uint64_t nr_pages, nr_pt_pages, nr_need_pages;
+  grub_uint64_t nr_need_pages;
+  grub_uint64_t try_virt_end;
+  struct grub_xen_mapping *map;
 
-  next_start.pt_base = max_addr + xen_inf.virt_base;
-  state.paging_start = max_addr >> PAGE_SHIFT;
+  map = mappings + n_mappings;
+  map_reloc = map + 1;
 
+  next_start.pt_base = max_addr + xen_inf.virt_base;
   nr_info_pages = max_addr >> PAGE_SHIFT;
-  nr_pages = nr_info_pages;
+  nr_need_pages = nr_info_pages;
 
   while (1)
     {
-      nr_pages = ALIGN_UP (nr_pages, (ALIGN_SIZE >> PAGE_SHIFT));
-      nr_pt_pages = get_pgtable_size (nr_pages, xen_inf.virt_base);
-      nr_need_pages =
-       nr_info_pages + nr_pt_pages +
-       ((ADDITIONAL_SIZE + STACK_SIZE) >> PAGE_SHIFT);
-      if (nr_pages >= nr_need_pages)
+      try_virt_end = ALIGN_UP (xen_inf.virt_base + page2offset (nr_need_pages) 
+
+                              ADDITIONAL_SIZE + STACK_SIZE, ALIGN_SIZE);
+      if (!xen_inf.virt_base)
+       try_virt_end += PAGE_SIZE;
+
+      err = get_pgtable_size (xen_inf.virt_base, try_virt_end, nr_info_pages);
+      if (err)
+       return err;
+      n_mappings++;
+
+      /* Map the relocator page either at virtual 0 or after end of area. */
+      nr_need_pages = nr_info_pages + map->area.n_pt_pages;
+      if (xen_inf.virt_base)
+       err = get_pgtable_size (0, PAGE_SIZE, nr_need_pages);
+      else
+       err = get_pgtable_size (try_virt_end - PAGE_SIZE, try_virt_end,
+                               nr_need_pages);
+      if (err)
+       return err;
+      nr_need_pages += map_reloc->area.n_pt_pages;
+
+      if (xen_inf.virt_base + page2offset (nr_need_pages) <= try_virt_end)
        break;
-      nr_pages = nr_need_pages;
+
+      n_mappings--;
     }
 
-  err = grub_relocator_alloc_chunk_addr (relocator, &ch,
-                                        max_addr, page2offset (nr_pt_pages));
+  n_mappings++;
+  nr_need_pages = map->area.n_pt_pages + map_reloc->area.n_pt_pages;
+  err = grub_relocator_alloc_chunk_addr (relocator, &ch, max_addr,
+                                        page2offset (nr_need_pages));
   if (err)
     return err;
 
-  virt_pgtable = get_virtual_current_address (ch);
-  pgtbl_start = max_addr >> PAGE_SHIFT;
-  max_addr += page2offset (nr_pt_pages);
+  map->where = get_virtual_current_address (ch);
+  map->area.pfn_start = 0;
+  max_addr += page2offset (nr_need_pages);
   state.stack = max_addr + STACK_SIZE + xen_inf.virt_base;
-  state.paging_size = nr_pt_pages;
-  next_start.nr_pt_frames = nr_pt_pages;
-  max_addr = page2offset (nr_pages);
-  pgtbl_end = nr_pages;
+  next_start.nr_pt_frames = nr_need_pages;
+  max_addr = try_virt_end - xen_inf.virt_base;
+  pgtbl_end = max_addr >> PAGE_SHIFT;
+  map_reloc->where = (grub_uint64_t *) ((char *) map->where +
+                                       page2offset (map->area.n_pt_pages));
 
   return GRUB_ERR_NONE;
 }
@@ -354,8 +463,8 @@ grub_xen_boot (void)
                (unsigned long long) xen_inf.virt_base,
                (unsigned long long) page2offset (nr_pages));
 
-  generate_page_table (virt_pgtable, pgtbl_start, pgtbl_end, nr_pages,
-                      xen_inf.virt_base, virt_mfn_list);
+  map_reloc->area.pfn_start = nr_pages;
+  generate_page_table (virt_mfn_list);
 
   state.entry_point = xen_inf.entry_point;
 
diff --git a/include/grub/xen/relocator.h b/include/grub/xen/relocator.h
index ae45dce..35a0ad9 100644
--- a/include/grub/xen/relocator.h
+++ b/include/grub/xen/relocator.h
@@ -23,11 +23,13 @@
 #include <grub/err.h>
 #include <grub/relocator.h>
 
+#define XEN_MAX_MAPPINGS 3
+
 struct grub_relocator_xen_state
 {
   grub_addr_t start_info;
-  grub_addr_t paging_start;
-  grub_addr_t paging_size;
+  grub_addr_t paging_start[XEN_MAX_MAPPINGS];
+  grub_addr_t paging_size[XEN_MAX_MAPPINGS];
   grub_addr_t mfn_list;
   grub_addr_t stack;
   grub_addr_t entry_point;
-- 
2.6.2




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