Re: [PATCH v2 1/3] hw/loongarch: Load FDT table into dram memory space

[gaosong]

在 2022/10/28 上午9:40, Xiaojuan Yang 写道:

Load FDT table into dram memory space, and the addr is 2 MiB.
Since lowmem region starts from 0, FDT base address is located
at 2 MiB to avoid NULL pointer access.

Signed-off-by: Xiaojuan Yang <yangxiaoj...@loongson.cn>
---
  hw/loongarch/virt.c         | 18 +++++++++++-------
  include/hw/loongarch/virt.h |  3 ---
  2 files changed, 11 insertions(+), 10 deletions(-)

Acked-by: Song Gao <gaos...@loongson.cn>

Thanks.
Song Gao

diff --git a/hw/loongarch/virt.c b/hw/loongarch/virt.c
index 29df99727d..fe33e7e3e4 100644
--- a/hw/loongarch/virt.c
+++ b/hw/loongarch/virt.c
@@ -159,7 +159,6 @@ static void fdt_add_pcie_node(const LoongArchMachineState 
*lams)
                                   1, FDT_PCI_RANGE_MMIO, 2, base_mmio,
                                   2, base_mmio, 2, size_mmio);
      g_free(nodename);
-    qemu_fdt_dumpdtb(ms->fdt, lams->fdt_size);
  }

static void fdt_add_irqchip_node(LoongArchMachineState *lams)

@@ -689,6 +688,7 @@ static void loongarch_init(MachineState *machine)
      MemoryRegion *address_space_mem = get_system_memory();
      LoongArchMachineState *lams = LOONGARCH_MACHINE(machine);
      int i;
+    hwaddr fdt_base;

if (!cpu_model) {

          cpu_model = LOONGARCH_CPU_TYPE_NAME("la464");
@@ -793,12 +793,16 @@ static void loongarch_init(MachineState *machine)
      lams->machine_done.notify = virt_machine_done;
      qemu_add_machine_init_done_notifier(&lams->machine_done);
      fdt_add_pcie_node(lams);
-
-    /* load fdt */
-    MemoryRegion *fdt_rom = g_new(MemoryRegion, 1);
-    memory_region_init_rom(fdt_rom, NULL, "fdt", VIRT_FDT_SIZE, &error_fatal);
-    memory_region_add_subregion(get_system_memory(), VIRT_FDT_BASE, fdt_rom);
-    rom_add_blob_fixed("fdt", machine->fdt, lams->fdt_size, VIRT_FDT_BASE);
+    /*
+     * Since lowmem region starts from 0, FDT base address is located
+     * at 2 MiB to avoid NULL pointer access.
+     *
+     * Put the FDT into the memory map as a ROM image: this will ensure
+     * the FDT is copied again upon reset, even if addr points into RAM.
+     */
+    fdt_base = 2 * MiB;
+    qemu_fdt_dumpdtb(machine->fdt, lams->fdt_size);
+    rom_add_blob_fixed("fdt", machine->fdt, lams->fdt_size, fdt_base);
  }

bool loongarch_is_acpi_enabled(LoongArchMachineState *lams)

diff --git a/include/hw/loongarch/virt.h b/include/hw/loongarch/virt.h
index 09f1c88ee5..45c383f5a7 100644
--- a/include/hw/loongarch/virt.h
+++ b/include/hw/loongarch/virt.h
@@ -28,9 +28,6 @@
  #define VIRT_GED_MEM_ADDR       (VIRT_GED_EVT_ADDR + ACPI_GED_EVT_SEL_LEN)
  #define VIRT_GED_REG_ADDR       (VIRT_GED_MEM_ADDR + MEMORY_HOTPLUG_IO_LEN)

-#define VIRT_FDT_BASE 0x1c400000

-#define VIRT_FDT_SIZE           0x100000
-
  struct LoongArchMachineState {
      /*< private >*/
      MachineState parent_obj;