[PATCH RESEND v2 2/2] xen/arm: Enlarge identity map space to 127TiB

[Leo Yan <leo.yan@xxxxxxxxxx>]

On some platforms, the memory regions could be:

  (XEN) MODULE[0]: 00000807f6df0000 - 00000807f6f3e000 Xen
  (XEN) MODULE[1]: 00000807f8054000 - 00000807f8056000 Device Tree
  (XEN) MODULE[2]: 00000000fa834000 - 00000000fc5de1d5 Ramdisk
  (XEN) MODULE[3]: 00000000fc5df000 - 00000000ffb3f810 Kernel

In this case, the Xen binary is loaded above 2TiB.  2TiB is the maximum
identity map space supported by Xen, thus it fails to boot up due to the
out of the range.

This patch introduces several macros to present the zeroth page table's
slot numbers for easier readable.  Based on the defined macros, it
enlarges identity map space to 127TiB, which can support the memory
space [0x0 .. 0x00007eff_ffff_ffff] so has flexibility for various
platforms.

Fixes: 1c78d76b67 ("xen/arm64: mm: Introduce helpers to prepare/enable/disable")
Reported-by: Alexey Klimov <alexey.klimov@xxxxxxxxxx>
Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
---
 xen/arch/arm/arm64/mm.c           | 12 ++++++++----
 xen/arch/arm/include/asm/config.h | 15 ++++++++-------
 xen/arch/arm/mm.c                 |  2 +-
 3 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/xen/arch/arm/arm64/mm.c b/xen/arch/arm/arm64/mm.c
index 78b7c7eb00..802170cf29 100644
--- a/xen/arch/arm/arm64/mm.c
+++ b/xen/arch/arm/arm64/mm.c
@@ -40,8 +40,10 @@ static void __init prepare_boot_identity_mapping(void)
     clear_page(boot_second_id);
     clear_page(boot_third_id);
 
-    if ( id_offsets[0] >= IDENTITY_MAPPING_AREA_NR_L0 )
-        panic("Cannot handle ID mapping above 2TB\n");
+    if ( id_offsets[0] >= XEN_IDENTITY_MAP_L0_END )
+        /* 1TiB occupies 2 slots in zeroeth table */
+        panic("Cannot handle ID mapping above %dTiB\n",
+              XEN_IDENTITY_MAP_L0_END>>1);
 
     /* Link first ID table */
     pte = mfn_to_xen_entry(virt_to_mfn(boot_first_id), MT_NORMAL);
@@ -73,8 +75,10 @@ static void __init prepare_runtime_identity_mapping(void)
     lpae_t pte;
     DECLARE_OFFSETS(id_offsets, id_addr);
 
-    if ( id_offsets[0] >= IDENTITY_MAPPING_AREA_NR_L0 )
-        panic("Cannot handle ID mapping above 2TB\n");
+    if ( id_offsets[0] >= XEN_IDENTITY_MAP_L0_END )
+        /* 1TiB occupies 2 slots in zeroeth table */
+        panic("Cannot handle ID mapping above %dTiB\n",
+              XEN_IDENTITY_MAP_L0_END>>1);
 
     /* Link first ID table */
     pte = pte_of_xenaddr((vaddr_t)xen_first_id);
diff --git a/xen/arch/arm/include/asm/config.h 
b/xen/arch/arm/include/asm/config.h
index 21f4e68a40..b772f1574d 100644
--- a/xen/arch/arm/include/asm/config.h
+++ b/xen/arch/arm/include/asm/config.h
@@ -87,11 +87,11 @@
  *   2G -   4G   Domheap: on-demand-mapped
  *
  * ARM64 layout:
- * 0x0000000000000000 - 0x000001ffffffffff (2TB, L0 slots [0..3])
+ * 0x0000000000000000 - 0x00007effffffffff (127TB, L0 slots [0..253])
  *
  *  Reserved to identity map Xen
  *
- * 0x0000020000000000 - 0x0000027fffffffff (512GB, L0 slot [4])
+ * 0x000007f000000000 - 0x00007fffffffffff (1TB, L0 slot [254..255])
  *  (Relative offsets)
  *   0  -   2M   Unmapped
  *   2M -  10M   Xen text, data, bss
@@ -103,9 +103,6 @@
  *
  *  32G -  64G   Frametable: 56 bytes per page for 2TB of RAM
  *
- * 0x0000028000000000 - 0x00007fffffffffff (125TB, L0 slots [5..255])
- *  Unused
- *
  * 0x0000800000000000 - 0x000084ffffffffff (5TB, L0 slots [256..265])
  *  1:1 mapping of RAM
  *
@@ -117,8 +114,12 @@
 #define XEN_VIRT_START          _AT(vaddr_t, MB(2))
 #else
 
-#define IDENTITY_MAPPING_AREA_NR_L0    4
-#define XEN_VM_MAPPING                 SLOT0(IDENTITY_MAPPING_AREA_NR_L0)
+#define XEN_IDENTITY_MAP_L0_START       0
+#define XEN_IDENTITY_MAP_L0_NUM         254
+#define XEN_IDENTITY_MAP_L0_END         (XEN_IDENTITY_MAP_L0_START + \
+                                         XEN_IDENTITY_MAP_L0_NUM)
+#define XEN_VM_MAP_L0_START             (XEN_IDENTITY_MAP_L0_END)
+#define XEN_VM_MAPPING                  SLOT0(XEN_VM_MAP_L0_START)
 
 #define SLOT0_ENTRY_BITS  39
 #define SLOT0(slot) (_AT(vaddr_t,slot) << SLOT0_ENTRY_BITS)
diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index c34cc94c90..218552783e 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -156,7 +156,7 @@ static void __init __maybe_unused build_assertions(void)
      * with it.
      */
 #define CHECK_OVERLAP_WITH_IDMAP(virt) \
-    BUILD_BUG_ON(zeroeth_table_offset(virt) < IDENTITY_MAPPING_AREA_NR_L0)
+    BUILD_BUG_ON(zeroeth_table_offset(virt) < XEN_IDENTITY_MAP_L0_END)
 
     CHECK_OVERLAP_WITH_IDMAP(XEN_VIRT_START);
     CHECK_OVERLAP_WITH_IDMAP(VMAP_VIRT_START);
-- 
2.39.2