Re: [PATCH v2 7/8] hw/mips/fuloong2e: Add highmem support

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

On 12/19/20 8:23 AM, Jiaxun Yang wrote:
> highmem started from 0x20000000.

"started from" -> "starts at"?

> Now we can have up to 2G RAM.
> 
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> ---
> v2: Handle SPD for dual DIMM correctly.
> ---
>  hw/mips/fuloong2e.c | 61 ++++++++++++++++++++++++++++++++++++---------
>  1 file changed, 49 insertions(+), 12 deletions(-)
> 
> diff --git a/hw/mips/fuloong2e.c b/hw/mips/fuloong2e.c
> index 2744b211fd..8a4bebe066 100644
> --- a/hw/mips/fuloong2e.c
> +++ b/hw/mips/fuloong2e.c
> @@ -56,6 +56,7 @@
>  /* Fuloong 2e has a 512k flash: Winbond W39L040AP70Z */
>  #define BIOS_SIZE               (512 * KiB)
>  #define MAX_IDE_BUS             2
> +#define HIGHMEM_START           0x20000000
>  
>  /*
>   * PMON is not part of qemu and released with BSD license, anyone
> @@ -71,7 +72,8 @@
>  #define FULOONG2E_RTL8139_SLOT    7
>  
>  static struct _loaderparams {
> -    int ram_size;
> +    int ram_low_size;
> +    int ram_high_size;
>      const char *kernel_filename;
>      const char *kernel_cmdline;
>      const char *initrd_filename;
> @@ -128,14 +130,14 @@ static uint64_t load_kernel(MIPSCPU *cpu)
>          initrd_size = get_image_size(loaderparams.initrd_filename);
>          if (initrd_size > 0) {
>              initrd_offset = ROUND_UP(kernel_high, INITRD_PAGE_SIZE);
> -            if (initrd_offset + initrd_size > loaderparams.ram_size) {
> +            if (initrd_offset + initrd_size > loaderparams.ram_low_size) {
>                  error_report("memory too small for initial ram disk '%s'",
>                               loaderparams.initrd_filename);
>                  exit(1);
>              }
>              initrd_size = load_image_targphys(loaderparams.initrd_filename,
>                                                initrd_offset,
> -                                              loaderparams.ram_size - initrd_offset);
> +                                              loaderparams.ram_low_size - initrd_offset);
>          }
>          if (initrd_size == (target_ulong) -1) {
>              error_report("could not load initial ram disk '%s'",
> @@ -160,7 +162,11 @@ static uint64_t load_kernel(MIPSCPU *cpu)
>  
>      /* Setup minimum environment variables */
>      prom_set(prom_buf, index++, "cpuclock=%u", clock_get_hz(cpu->clock));
> -    prom_set(prom_buf, index++, "memsize=%"PRIi64, loaderparams.ram_size / MiB);
> +    prom_set(prom_buf, index++, "memsize=%"PRIi64, loaderparams.ram_low_size / MiB);
> +    if (loaderparams.ram_high_size > 0) {
> +            prom_set(prom_buf, index++, "highmemsize=%"PRIi64,
> +                    loaderparams.ram_high_size / MiB);
> +    }
>      prom_set(prom_buf, index++, NULL);
>  
>      rom_add_blob_fixed("prom", prom_buf, prom_size, ENVP_PADDR);
> @@ -186,7 +192,7 @@ static void write_bootloader(CPUMIPSState *env, uint8_t *base,
>      p = (uint32_t *)(base + 0x040);
>  
>      bl_gen_jump_kernel(&p, ENVP_VADDR - 64, 2, ENVP_VADDR,
> -                       ENVP_VADDR + 8, loaderparams.ram_size,
> +                       ENVP_VADDR + 8, loaderparams.ram_low_size,
>                         kernel_addr);
>  }
>  
> @@ -258,8 +264,11 @@ static void mips_fuloong2e_init(MachineState *machine)
>      const char *kernel_filename = machine->kernel_filename;
>      const char *kernel_cmdline = machine->kernel_cmdline;
>      const char *initrd_filename = machine->initrd_filename;
> +    ram_addr_t ram_low_size, ram_high_size = 0;
>      char *filename;
>      MemoryRegion *address_space_mem = get_system_memory();
> +    MemoryRegion *ram_low_alias = g_new(MemoryRegion, 1);
> +    MemoryRegion *ram_high_alias;
>      MemoryRegion *bios = g_new(MemoryRegion, 1);
>      long bios_size;
>      uint8_t *spd_data;
> @@ -282,12 +291,31 @@ static void mips_fuloong2e_init(MachineState *machine)
>  
>      qemu_register_reset(main_cpu_reset, cpu);
>  
> -    /* TODO: support more than 256M RAM as highmem */
> -    if (machine->ram_size != 256 * MiB) {
> -        error_report("Invalid RAM size, should be 256MB");
> +    if (machine->ram_size > 2 * GiB) {
> +        error_report("Too much memory for this machine: %" PRId64 "MB,"
> +                     " maximum 2048MB", machine->ram_size / MiB);
>          exit(EXIT_FAILURE);
>      }
> -    memory_region_add_subregion(address_space_mem, 0, machine->ram);
> +
> +    ram_low_size = MIN(machine->ram_size, 256 * MiB);
> +
> +    memory_region_init_alias(ram_low_alias, NULL,
> +                            "ram_low_alias",
> +                            machine->ram, 0,
> +                            ram_low_size);
> +    memory_region_add_subregion(address_space_mem, 0,
> +                                ram_low_alias);
> +
> +    if (machine->ram_size > 256 * MiB) {
> +        ram_high_alias = g_new(MemoryRegion, 1);
> +        ram_high_size = machine->ram_size - ram_low_size;
> +        memory_region_init_alias(ram_high_alias, NULL,
> +                                "ram_high_alias",
> +                                machine->ram, ram_low_size,
> +                                ram_high_size);
> +        memory_region_add_subregion(address_space_mem, HIGHMEM_START,
> +                                    ram_high_alias);

Cool, I've been using the same patch for one year. It works fine with
a Linux kernel which doesn't change the northbridge mapping. As there
is no plan for using another bootloader than PMON with this machine,
that is fine.

> +    }
>  
>      /* Boot ROM */
>      memory_region_init_rom(bios, NULL, "fuloong2e.bios", BIOS_SIZE,
> @@ -300,7 +328,8 @@ static void mips_fuloong2e_init(MachineState *machine)
>       */
>  
>      if (kernel_filename) {
> -        loaderparams.ram_size = machine->ram_size;
> +        loaderparams.ram_low_size = ram_low_size;
> +        loaderparams.ram_high_size = ram_high_size;
>          loaderparams.kernel_filename = kernel_filename;
>          loaderparams.kernel_cmdline = kernel_cmdline;
>          loaderparams.initrd_filename = initrd_filename;
> @@ -345,8 +374,16 @@ static void mips_fuloong2e_init(MachineState *machine)
>      }
>  
>      /* Populate SPD eeprom data */
> -    spd_data = spd_data_generate(DDR, machine->ram_size);
> -    smbus_eeprom_init_one(smbus, 0x50, spd_data);
> +    if (machine->ram_size <= 1 * GiB) {
> +        /* It supports maxium of 1 GiB per DIMM */

Typo "maximum".

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

> +        spd_data = spd_data_generate(DDR, machine->ram_size);
> +        smbus_eeprom_init_one(smbus, 0x50, spd_data);
> +    } else {
> +        /* Split to dual DIMM for more than 1 GiB  */
> +        spd_data = spd_data_generate(DDR, machine->ram_size / 2);
> +        smbus_eeprom_init_one(smbus, 0x50, spd_data);
> +        smbus_eeprom_init_one(smbus, 0x51, spd_data);
> +    }
>  
>      mc146818_rtc_init(isa_bus, 2000, NULL);
>  
>