hw/openrisc: Support monitor dumpdtb command

The openrisc machines don't set MachineState::fdt to point to their
DTB blob.  This means that although the command line '-machine
dumpdtb=file.dtb' option works, the equivalent QMP and HMP monitor
commands do not, but instead produce the error "This machine doesn't
have a FDT".

Set MachineState::fdt in openrisc_load_fdt(), when we write it to
guest memory.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20250206151214.2947842-3-peter.maydell@linaro.org

hw/openrisc/boot.c

@@ -90,8 +90,8 @@ hwaddr openrisc_load_initrd(void *fdt, const char *filename,
     return start + size;
 }
 
-uint32_t openrisc_load_fdt(void *fdt, hwaddr load_start,
-                           uint64_t mem_size)
+uint32_t openrisc_load_fdt(MachineState *ms, void *fdt,
+                           hwaddr load_start, uint64_t mem_size)
 {
     uint32_t fdt_addr;
     int ret;
@@ -111,6 +111,9 @@ uint32_t openrisc_load_fdt(void *fdt, hwaddr load_start,
     /* copy in the device tree */
     qemu_fdt_dumpdtb(fdt, fdtsize);
 
+    /* Save FDT for dumpdtb monitor command */
+    ms->fdt = fdt;
+
     rom_add_blob_fixed_as("fdt", fdt, fdtsize, fdt_addr,
                           &address_space_memory);
     qemu_register_reset_nosnapshotload(qemu_fdt_randomize_seeds,

hw/openrisc/openrisc_sim.c

@@ -354,7 +354,7 @@ static void openrisc_sim_init(MachineState *machine)
                                              machine->initrd_filename,
                                              load_addr, machine->ram_size);
         }
-        boot_info.fdt_addr = openrisc_load_fdt(state->fdt, load_addr,
+        boot_info.fdt_addr = openrisc_load_fdt(machine, state->fdt, load_addr,
                                                machine->ram_size);
     }
 }

hw/openrisc/virt.c

@@ -540,7 +540,7 @@ static void openrisc_virt_init(MachineState *machine)
                                              machine->initrd_filename,
                                              load_addr, machine->ram_size);
         }
-        boot_info.fdt_addr = openrisc_load_fdt(state->fdt, load_addr,
+        boot_info.fdt_addr = openrisc_load_fdt(machine, state->fdt, load_addr,
                                                machine->ram_size);
     }
 }

include/hw/openrisc/boot.h

@@ -20,6 +20,7 @@
 #define OPENRISC_BOOT_H
 
 #include "exec/cpu-defs.h"
+#include "hw/boards.h"
 
 hwaddr openrisc_load_kernel(ram_addr_t ram_size,
                             const char *kernel_filename,
@@ -28,7 +29,7 @@ hwaddr openrisc_load_kernel(ram_addr_t ram_size,
 hwaddr openrisc_load_initrd(void *fdt, const char *filename,
                             hwaddr load_start, uint64_t mem_size);
 
-uint32_t openrisc_load_fdt(void *fdt, hwaddr load_start,
+uint32_t openrisc_load_fdt(MachineState *ms, void *fdt, hwaddr load_start,
                            uint64_t mem_size);
 
 #endif /* OPENRISC_BOOT_H */