[Qemu-devel] [PATCH v2] pc_sysfw: Always use alias for ISA BIOS region

[Jan Kiszka <jan.kiszka@siemens.com>]

This is no technical reason (anymore) for copying the ISA BIOS from the
original region. Instead, refactor pc_isa_bios_init to serve both pflash
and old-style BIOS setup.

Unfortunately, the previous RAM-backed version created an additional
vmstate section, content-wise redundant to the BIOS, but we still need
to process it when working in compat mode.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---

Changes in v2:
 - create dummy vmstate section to enable migration from 1.1/1.2

 hw/pc_piix.c  |    4 ++++
 hw/pc_sysfw.c |   55 +++++++++++++++++++++----------------------------------
 2 files changed, 25 insertions(+), 34 deletions(-)

diff --git a/hw/pc_piix.c b/hw/pc_piix.c
index cfa839c..0051b2a 100644
--- a/hw/pc_piix.c
+++ b/hw/pc_piix.c
@@ -386,6 +386,10 @@ static QEMUMachine pc_machine_v1_3 = {
             .driver   = "VGA",\
             .property = "mmio",\
             .value    = "off",\
+        },{\
+            .driver   = "pc-sysfw",\
+            .property = "compat_vmsection",\
+            .value    = "on",\
         }
 
 static QEMUMachine pc_machine_v1_2 = {
diff --git a/hw/pc_sysfw.c b/hw/pc_sysfw.c
index 9d7c5f4..a60f453 100644
--- a/hw/pc_sysfw.c
+++ b/hw/pc_sysfw.c
@@ -38,40 +38,36 @@
 typedef struct PcSysFwDevice {
     SysBusDevice busdev;
     uint8_t rom_only;
+    uint32_t compat_vmsection;
 } PcSysFwDevice;
 
 static void pc_isa_bios_init(MemoryRegion *rom_memory,
-                             MemoryRegion *flash_mem,
-                             int ram_size)
+                             MemoryRegion *bios, bool compat_vmsection)
 {
+    uint64_t bios_size = memory_region_size(bios);
     int isa_bios_size;
     MemoryRegion *isa_bios;
-    uint64_t flash_size;
-    void *flash_ptr, *isa_bios_ptr;
-
-    flash_size = memory_region_size(flash_mem);
 
     /* map the last 128KB of the BIOS in ISA space */
-    isa_bios_size = flash_size;
+    isa_bios_size = bios_size;
     if (isa_bios_size > (128 * 1024)) {
         isa_bios_size = 128 * 1024;
     }
     isa_bios = g_malloc(sizeof(*isa_bios));
-    memory_region_init_ram(isa_bios, "isa-bios", isa_bios_size);
-    vmstate_register_ram_global(isa_bios);
+    memory_region_init_alias(isa_bios, "isa-bios", bios,
+                             bios_size - isa_bios_size, isa_bios_size);
     memory_region_add_subregion_overlap(rom_memory,
                                         0x100000 - isa_bios_size,
                                         isa_bios,
                                         1);
+    memory_region_set_readonly(isa_bios, true);
 
-    /* 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);
+    if (compat_vmsection) {
+        MemoryRegion *dummy_region = g_new(MemoryRegion, 1);
 
-    memory_region_set_readonly(isa_bios, true);
+        memory_region_init_ram(dummy_region, "isa-bios", isa_bios_size);
+        vmstate_register_ram_global(dummy_region);
+    }
 }
 
 static void pc_fw_add_pflash_drv(void)
@@ -102,7 +98,7 @@ static void pc_fw_add_pflash_drv(void)
 }
 
 static void pc_system_flash_init(MemoryRegion *rom_memory,
-                                 DriveInfo *pflash_drv)
+                                 DriveInfo *pflash_drv, bool compat_vmsection)
 {
     BlockDriverState *bdrv;
     int64_t size;
@@ -129,14 +125,14 @@ static void pc_system_flash_init(MemoryRegion *rom_memory,
                                          1, 0x0000, 0x0000, 0x0000, 0x0000, 0);
     flash_mem = pflash_cfi01_get_memory(system_flash);
 
-    pc_isa_bios_init(rom_memory, flash_mem, size);
+    pc_isa_bios_init(rom_memory, flash_mem, compat_vmsection);
 }
 
 static void old_pc_system_rom_init(MemoryRegion *rom_memory)
 {
     char *filename;
-    MemoryRegion *bios, *isa_bios;
-    int bios_size, isa_bios_size;
+    MemoryRegion *bios;
+    int bios_size;
     int ret;
 
     /* BIOS load */
@@ -167,19 +163,7 @@ static void old_pc_system_rom_init(MemoryRegion *rom_memory)
         g_free(filename);
     }
 
-    /* map the last 128KB of the BIOS in ISA space */
-    isa_bios_size = bios_size;
-    if (isa_bios_size > (128 * 1024)) {
-        isa_bios_size = 128 * 1024;
-    }
-    isa_bios = g_malloc(sizeof(*isa_bios));
-    memory_region_init_alias(isa_bios, "isa-bios", bios,
-                             bios_size - isa_bios_size, isa_bios_size);
-    memory_region_add_subregion_overlap(rom_memory,
-                                        0x100000 - isa_bios_size,
-                                        isa_bios,
-                                        1);
-    memory_region_set_readonly(isa_bios, true);
+    pc_isa_bios_init(rom_memory, bios, false);
 
     /* map all the bios at the top of memory */
     memory_region_add_subregion(rom_memory,
@@ -224,7 +208,8 @@ void pc_system_firmware_init(MemoryRegion *rom_memory)
     }
 
     if (pflash_drv != NULL) {
-        pc_system_flash_init(rom_memory, pflash_drv);
+        pc_system_flash_init(rom_memory, pflash_drv,
+                             sysfw_dev->compat_vmsection);
     } else {
         fprintf(stderr, "qemu: PC system firmware (pflash) not available\n");
         exit(1);
@@ -233,6 +218,8 @@ void pc_system_firmware_init(MemoryRegion *rom_memory)
 
 static Property pcsysfw_properties[] = {
     DEFINE_PROP_UINT8("rom_only", PcSysFwDevice, rom_only, 0),
+    DEFINE_PROP_BIT("compat_vmsection", PcSysFwDevice, compat_vmsection, 0,
+                    false),
     DEFINE_PROP_END_OF_LIST(),
 };
 
-- 
1.7.3.4