[PATCH RESEND v2 18/32] hw/i386/pc_sysfw: Simplify using memory_region_init_alias()

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

The scripts/coccinelle/memory-region-housekeeping.cocci reported:
* TODO [[view:hw/i386/pc_sysfw.c::face=ovl-face1::linb=67::colb=4::cole=26][potential use of memory_region_init_rom*() in  hw/i386/pc_sysfw.c::67]]

pc_isa_bios_init() does a manual copy of a part of the BIOS,
from a read-only region. We can simplify by directly aliasing
the same part.

Before:

  (qemu) info mtree
  memory-region: system
    0000000000000000-ffffffffffffffff (prio 0, i/o): system
      0000000000000000-0000000007ffffff (prio 0, ram): alias ram-below-4g @pc.ram 0000000000000000-0000000007ffffff
      0000000000000000-ffffffffffffffff (prio -1, i/o): pci
        00000000000a0000-00000000000bffff (prio 1, i/o): vga-lowmem
        00000000000c0000-00000000000dffff (prio 1, rom): pc.rom
        00000000000e0000-00000000000fffff (prio 1, rom): isa-bios
      ...
      00000000fff00000-00000000ffffffff (prio 0, romd): system.flash0

After:

  (qemu) info mtree
  memory-region: system
    0000000000000000-ffffffffffffffff (prio 0, i/o): system
      0000000000000000-0000000007ffffff (prio 0, ram): alias ram-below-4g @pc.ram 0000000000000000-0000000007ffffff
      0000000000000000-ffffffffffffffff (prio -1, i/o): pci
        00000000000a0000-00000000000bffff (prio 1, i/o): vga-lowmem
        00000000000c0000-00000000000dffff (prio 1, rom): pc.rom
        00000000000e0000-00000000000fffff (prio 1, romd): alias isa-bios @system.flash0 00000000000e0000-00000000000fffff
      ...
      00000000fff00000-00000000ffffffff (prio 0, romd): system.flash0

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 hw/i386/pc_sysfw.c | 24 ++++++------------------
 1 file changed, 6 insertions(+), 18 deletions(-)

diff --git a/hw/i386/pc_sysfw.c b/hw/i386/pc_sysfw.c
index f5f3f466b0..e864c09ea8 100644
--- a/hw/i386/pc_sysfw.c
+++ b/hw/i386/pc_sysfw.c
@@ -54,31 +54,19 @@ static void pc_isa_bios_init(MemoryRegion *rom_memory,
                              MemoryRegion *flash_mem,
                              int ram_size)
 {
-    int isa_bios_size;
-    MemoryRegion *isa_bios;
-    uint64_t flash_size;
-    void *flash_ptr, *isa_bios_ptr;
-
-    flash_size = memory_region_size(flash_mem);
+    uint64_t isa_bios_size;
+    MemoryRegion *isa_bios = g_new(MemoryRegion, 1);
+    uint64_t flash_size = memory_region_size(flash_mem);
 
     /* map the last 128KB of the BIOS in ISA space */
     isa_bios_size = MIN(flash_size, 128 * KiB);
-    isa_bios = g_malloc(sizeof(*isa_bios));
-    memory_region_init_ram(isa_bios, NULL, "isa-bios", isa_bios_size,
-                           &error_fatal);
+    memory_region_init_alias(isa_bios, NULL, "isa-bios", flash_mem,
+                             flash_size - isa_bios_size,
+                             isa_bios_size);
     memory_region_add_subregion_overlap(rom_memory,
                                         0x100000 - isa_bios_size,
                                         isa_bios,
                                         1);
-
-    /* copy ISA rom image from top of flash memory */
-    flash_ptr = memory_region_get_ram_ptr(flash_mem);
-    isa_bios_ptr = memory_region_get_ram_ptr(isa_bios);
-    memcpy(isa_bios_ptr,
-           ((uint8_t*)flash_ptr) + (flash_size - isa_bios_size),
-           isa_bios_size);
-
-    memory_region_set_readonly(isa_bios, true);
 }
 
 static PFlashCFI01 *pc_pflash_create(PCMachineState *pcms,
-- 
2.21.1