Re: [PATCH v2 1/5] mac_oldworld: Allow loading binary ROM image

[BALATON Zoltan]

On Sun, 14 Jun 2020, Mark Cave-Ayland wrote:
> On 13/06/2020 14:36, BALATON Zoltan wrote:
>
> > The G3 beige machine has a 4MB firmware ROM. Fix the size of the rom
> > region and allow loading a binary image with -bios. This makes it
> > possible to test emulation with a ROM image from real hardware.
> >
> > Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
> > ---
> >  hw/ppc/mac_oldworld.c | 24 +++++++++++++++---------
> >  1 file changed, 15 insertions(+), 9 deletions(-)
> >
> > diff --git a/hw/ppc/mac_oldworld.c b/hw/ppc/mac_oldworld.c
> > index 0b4c1c6373..3812adc441 100644
> > --- a/hw/ppc/mac_oldworld.c
> > +++ b/hw/ppc/mac_oldworld.c
> > @@ -59,6 +59,8 @@
> >  #define NDRV_VGA_FILENAME "qemu_vga.ndrv"
> >
> >  #define GRACKLE_BASE 0xfec00000
> > +#define PROM_BASE 0xffc00000
> > +#define PROM_SIZE (4 * MiB)
> >
> >  static void fw_cfg_boot_set(void *opaque, const char *boot_device,
> >                              Error **errp)
> > @@ -127,24 +129,28 @@ static void ppc_heathrow_init(MachineState *machine)
> >
> >      memory_region_add_subregion(sysmem, 0, machine->ram);
> >
> > -    /* allocate and load BIOS */
> > -    memory_region_init_rom(bios, NULL, "ppc_heathrow.bios", BIOS_SIZE,
> > +    /* allocate and load firmware ROM */
> > +    memory_region_init_rom(bios, NULL, "ppc_heathrow.bios", PROM_SIZE,
> >                             &error_fatal);
> > +    memory_region_add_subregion(sysmem, PROM_BASE, bios);
> >
> > -    if (bios_name == NULL)
> > +    if (!bios_name) {
> >          bios_name = PROM_FILENAME;
> > +    }
> >      filename = qemu_find_file(QEMU_FILE_TYPE_BIOS, bios_name);
> > -    memory_region_add_subregion(sysmem, PROM_ADDR, bios);
> > -
> > -    /* Load OpenBIOS (ELF) */
> >      if (filename) {
> > -        bios_size = load_elf(filename, NULL, 0, NULL, NULL, NULL, NULL, NULL,
> > -                             1, PPC_ELF_MACHINE, 0, 0);
> > +        /* Load OpenBIOS (ELF) */
> > +        bios_size = load_elf(filename, NULL, NULL, NULL, NULL, NULL, NULL,
> > +                             NULL, 1, PPC_ELF_MACHINE, 0, 0);
> > +        if (bios_size <= 0) {
> > +            /* or load binary ROM image */
> > +            bios_size = load_image_targphys(filename, PROM_BASE, PROM_SIZE);
> > +        }
> >          g_free(filename);
> >      } else {
> >          bios_size = -1;
> >      }
> > -    if (bios_size < 0 || bios_size > BIOS_SIZE) {
> > +    if (bios_size < 0 || bios_size > PROM_SIZE) {
> >          error_report("could not load PowerPC bios '%s'", bios_name);
> >          exit(1);
> >      }
>
> I think the logic could be improved a bit here: load_elf() can return the 
> physical
> address from the ELF, so it would make sense to use that as the address for
> load_image_targphys() if present, and otherwise fall back to loading at 
> 0xffc00000.

I don't get this. No need to do it that way because load_elf already loads 
the image at address specified in ELF file (I guess because it still works 
with OpenBIOS after this patch) so don't have to call load_image_targphys 
for that case. The above tries load_elf and only if it did not succeed 
calls load_image_targphys to load a binary image to fill the ROM. I don't 
see how this logic could be simpler.

Maybe we need the load address from the ELF to check if an ELF would 
overflow the region as in elf_addr + bios_size > PROM_ADDR + PROM_SIZE but 
I'm not sure. Any suggestion?

> It may also make sense to split PROM_ADDR to PROM_ADDR_OLDWORLD and
> PROM_ADDR_NEWWORLD (and similar for BIOS_SIZE) to allow these values to be 
> adjusted
> separately for each machine.

BIOS_SIZE is not used in this board after this patch any more so that's 
basically PROM_SIZE_NEWWORLD now which can be defined in mac_newworld and 
removed from mac.h. Then we have separate PROM_SIZE for each board. I've 
also defined PROM_ADDR here in mac_oldworld and similar define can be 
added to mac_newworld if needed. These should not be in mac.h I think as 
these are board specific. I regard the previous BIOS_* values specific to 
OpenBIOS not to boards so now that boards can use other ROMs not just 
OpenBIOS BIOS_SIZE may not be needed, what we need is the size of the ROM 
chip on board instead.

Regards,
BALATON Zoltan