Align guest physical address and host physical address
beyond guest 4GB on a 1GB boundary, in case hugetlbfs is used.

Otherwise 1GB TLBs cannot be cached for the range.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: qemu/hw/i386/pc.c
===================================================================
--- qemu.orig/hw/i386/pc.c
+++ qemu/hw/i386/pc.c
@@ -1116,8 +1116,9 @@ FWCfgState *pc_memory_init(MemoryRegion
 {
     int linux_boot, i;
     MemoryRegion *ram, *option_rom_mr;
-    MemoryRegion *ram_below_4g, *ram_above_4g;
+    MemoryRegion *ram_below_4g, *ram_above_4g, *ram_above_4g_piecetwo;
     FWCfgState *fw_cfg;
+    unsigned long hpagesize;
 
     linux_boot = (kernel_filename != NULL);
 
@@ -1129,6 +1130,7 @@ FWCfgState *pc_memory_init(MemoryRegion
     memory_region_init_ram(ram, NULL, "pc.ram",
                            below_4g_mem_size + above_4g_mem_size);
     vmstate_register_ram_global(ram);
+    hpagesize = qemu_get_ram_hpagesize(ram->ram_addr);
     *ram_memory = ram;
     ram_below_4g = g_malloc(sizeof(*ram_below_4g));
     memory_region_init_alias(ram_below_4g, NULL, "ram-below-4g", ram,
@@ -1136,10 +1138,46 @@ FWCfgState *pc_memory_init(MemoryRegion
     memory_region_add_subregion(system_memory, 0, ram_below_4g);
     if (above_4g_mem_size > 0) {
         ram_above_4g = g_malloc(sizeof(*ram_above_4g));
-        memory_region_init_alias(ram_above_4g, NULL, "ram-above-4g", ram,
-                                 below_4g_mem_size, above_4g_mem_size);
-        memory_region_add_subregion(system_memory, 0x100000000ULL,
+
+        /*
+         *
+         * If 1GB hugepages are used to back guest RAM, map guest address
+         * space in the range [ramsize,ramsize+holesize] to the ram block
+         * range [holestart, 4GB]
+         *
+         *                      0      h     4G     [ramsize,ramsize+holesize]
+         *
+         * guest-addr-space     [      ]     [      ][xxx]
+         *                                /----------/
+         * contiguous-ram-block [      ][xxx][     ]
+         *
+         * So that memory beyond 4GB is aligned on a 1GB boundary,
+         * at the host physical address space.
+         *
+         */
+        if (hpagesize == (1<<30)) {
+            unsigned long holesize = 0x100000000ULL - below_4g_mem_size;
+
+            memory_region_init_alias(ram_above_4g, NULL, "ram-above-4g", ram,
+                                    0x100000000ULL,
+                                    above_4g_mem_size - holesize);
+            memory_region_add_subregion(system_memory, 0x100000000ULL,
+                                    ram_above_4g);
+
+            ram_above_4g_piecetwo = g_malloc(sizeof(*ram_above_4g_piecetwo));
+            memory_region_init_alias(ram_above_4g_piecetwo, NULL,
+                                     "ram-above-4g-piecetwo", ram,
+                                     0x100000000ULL - holesize, holesize);
+            memory_region_add_subregion(system_memory,
+                                        0x100000000ULL +
+                                        above_4g_mem_size - holesize,
+                                        ram_above_4g_piecetwo);
+        } else {
+            memory_region_init_alias(ram_above_4g, NULL, "ram-above-4g", ram,
+                                    below_4g_mem_size, above_4g_mem_size);
+            memory_region_add_subregion(system_memory, 0x100000000ULL,
                                     ram_above_4g);
+        }
     }