From 6997f26d0dfd11f27a42caa04c3a20287452f364 Mon Sep 17 00:00:00 2001 From: Mark Cave-Ayland Date: Wed, 4 Oct 2023 09:37:52 +0100 Subject: [PATCH] q800: allow accesses to RAM area even if less memory is available MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit MacOS attempts a series of writes and reads over the entire RAM area in order to determine the amount of RAM within the machine. Allow accesses to the entire RAM area ignoring writes and always reading zero for areas where there is no physical RAM installed to allow MacOS to detect the memory size without faulting. Signed-off-by: Mark Cave-Ayland Reviewed-by: Philippe Mathieu-Daudé Reviewed-by: Laurent Vivier Message-ID: <20231004083806.757242-7-mark.cave-ayland@ilande.co.uk> Signed-off-by: Laurent Vivier --- hw/m68k/q800.c | 30 +++++++++++++++++++++++++++++- include/hw/m68k/q800.h | 1 + 2 files changed, 30 insertions(+), 1 deletion(-) diff --git a/hw/m68k/q800.c b/hw/m68k/q800.c index 081b95e9cf..3209309173 100644 --- a/hw/m68k/q800.c +++ b/hw/m68k/q800.c @@ -86,6 +86,9 @@ #define MAC_CLOCK 3686418 +/* Size of whole RAM area */ +#define RAM_SIZE 0x40000000 + /* * Slot 0x9 is reserved for use by the in-built framebuffer whilst only * slots 0xc, 0xd and 0xe physically exist on the Quadra 800 @@ -218,6 +221,27 @@ static const MemoryRegionOps machine_id_ops = { }, }; +static uint64_t ramio_read(void *opaque, hwaddr addr, unsigned size) +{ + return 0x0; +} + +static void ramio_write(void *opaque, hwaddr addr, uint64_t val, + unsigned size) +{ + return; +} + +static const MemoryRegionOps ramio_ops = { + .read = ramio_read, + .write = ramio_write, + .endianness = DEVICE_BIG_ENDIAN, + .valid = { + .min_access_size = 1, + .max_access_size = 4, + }, +}; + static void q800_machine_init(MachineState *machine) { Q800MachineState *m = Q800_MACHINE(machine); @@ -262,7 +286,11 @@ static void q800_machine_init(MachineState *machine) qemu_register_reset(main_cpu_reset, &m->cpu); /* RAM */ - memory_region_add_subregion(get_system_memory(), 0, machine->ram); + memory_region_init_io(&m->ramio, OBJECT(machine), &ramio_ops, &m->ramio, + "ram", RAM_SIZE); + memory_region_add_subregion(get_system_memory(), 0x0, &m->ramio); + + memory_region_add_subregion(&m->ramio, 0, machine->ram); /* * Create container for all IO devices diff --git a/include/hw/m68k/q800.h b/include/hw/m68k/q800.h index 98097165d9..04e4e0bce3 100644 --- a/include/hw/m68k/q800.h +++ b/include/hw/m68k/q800.h @@ -60,6 +60,7 @@ struct Q800MachineState { MacfbNubusState macfb; DJMEMCState djmemc; IOSBState iosb; + MemoryRegion ramio; MemoryRegion macio; MemoryRegion macio_alias; MemoryRegion machine_id; -- 2.11.0