Re: [Qemu-devel] [PATCH v9 3/8] loader: Allow a custom AddressSpace when loading ROMs

[Alistair Francis]

On Fri, Jul 29, 2016 at 8:56 AM, Peter Maydell <address@hidden> wrote:
> On 14 July 2016 at 01:03, Alistair Francis <address@hidden> wrote:
>> When loading ROMs allow the caller to specify an AddressSpace to use for
>> the load.
>>
>> Signed-off-by: Alistair Francis <address@hidden>
>> ---
>> V9:
>>  - Fixup the ROM ordering
>>  - Don't allow address space and memory region to be specified
>> V8:
>>  - Introduce an RFC version of AddressSpace loading support
>>
>>  hw/core/loader.c     | 39 ++++++++++++++++++++++++++++-----------
>>  include/hw/elf_ops.h |  2 +-
>>  include/hw/loader.h  | 10 ++++++----
>>  3 files changed, 35 insertions(+), 16 deletions(-)
>>
>> diff --git a/hw/core/loader.c b/hw/core/loader.c
>> index 6b61f29..a024133 100644
>> --- a/hw/core/loader.c
>> +++ b/hw/core/loader.c
>> @@ -777,6 +777,7 @@ struct Rom {
>>
>>      uint8_t *data;
>>      MemoryRegion *mr;
>> +    AddressSpace *as;
>>      int isrom;
>>      char *fw_dir;
>>      char *fw_file;
>> @@ -796,12 +797,15 @@ static void rom_insert(Rom *rom)
>>          hw_error ("ROM images must be loaded at startup\n");
>>      }
>>
>> -    /* list is ordered by load address */
>> +    /* List is ordered by load address in the same address space */
>>      QTAILQ_FOREACH(item, &roms, next) {
>> -        if (rom->addr >= item->addr)
>> -            continue;
>> -        QTAILQ_INSERT_BEFORE(item, rom, next);
>> -        return;
>> +        if (rom->addr >= item->addr && rom->as == item->as) {
>> +            QTAILQ_INSERT_AFTER(&roms, item, rom, next);
>> +            return;
>> +        } else if (rom->addr <= item->addr && rom->as == item->as) {
>> +            QTAILQ_INSERT_BEFORE(item, rom, next);
>> +            return;
>> +        }
>>      }
>>      QTAILQ_INSERT_TAIL(&roms, rom, next);
>
> This seems a somewhat confusing way of writing this. I think you
> should define a comparison function and then just replace the
> current "rom->addr >= item->addr" with "rom_order_compare(rom, item) >= 0".
> Then it's clear what the comparison you're using to define the
> sorted order is and that the loop will put things in in sorted
> position.

I tidied this up so it is easier to read and am now using the
rom_order_compare() function.

>
>>  }
>> @@ -833,16 +837,25 @@ static void *rom_set_mr(Rom *rom, Object *owner, const 
>> char *name)
>>
>>  int rom_add_file(const char *file, const char *fw_dir,
>>                   hwaddr addr, int32_t bootindex,
>> -                 bool option_rom, MemoryRegion *mr)
>> +                 bool option_rom, MemoryRegion *mr,
>> +                 AddressSpace *as)
>>  {
>>      MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());
>>      Rom *rom;
>>      int rc, fd = -1;
>>      char devpath[100];
>>
>> +    if (as && mr) {
>> +        fprintf(stderr, "Specifying an Address Space and Memory Region is " 
>> \
>> +                "not valid when loading a rom\n");
>
> Some day we'll fix this up to use Errors, but that day need not be today.

Phew!

>
>> +        /* We haven't allocated anything so we don't need any cleanup */
>> +        return -1;
>> +    }
>> +
>>      rom = g_malloc0(sizeof(*rom));
>>      rom->name = g_strdup(file);
>>      rom->path = qemu_find_file(QEMU_FILE_TYPE_BIOS, rom->name);
>> +    rom->as = as;
>>      if (rom->path == NULL) {
>>          rom->path = g_strdup(file);
>>      }
>> @@ -969,7 +982,7 @@ MemoryRegion *rom_add_blob(const char *name, const void 
>> *blob, size_t len,
>>   * memory ownership of "data", so we don't have to allocate and copy the 
>> buffer.
>>   */
>>  int rom_add_elf_program(const char *name, void *data, size_t datasize,
>> -                        size_t romsize, hwaddr addr)
>> +                        size_t romsize, hwaddr addr, AddressSpace *as)
>>  {
>>      Rom *rom;
>>
>> @@ -979,18 +992,19 @@ int rom_add_elf_program(const char *name, void *data, 
>> size_t datasize,
>>      rom->datasize = datasize;
>>      rom->romsize  = romsize;
>>      rom->data     = data;
>> +    rom->as       = as;
>>      rom_insert(rom);
>>      return 0;
>>  }
>>
>>  int rom_add_vga(const char *file)
>>  {
>> -    return rom_add_file(file, "vgaroms", 0, -1, true, NULL);
>> +    return rom_add_file(file, "vgaroms", 0, -1, true, NULL, NULL);
>>  }
>>
>>  int rom_add_option(const char *file, int32_t bootindex)
>>  {
>> -    return rom_add_file(file, "genroms", 0, bootindex, true, NULL);
>> +    return rom_add_file(file, "genroms", 0, bootindex, true, NULL, NULL);
>>  }
>>
>>  static void rom_reset(void *unused)
>> @@ -1008,7 +1022,8 @@ static void rom_reset(void *unused)
>>              void *host = memory_region_get_ram_ptr(rom->mr);
>>              memcpy(host, rom->data, rom->datasize);
>>          } else {
>> -            cpu_physical_memory_write_rom(&address_space_memory,
>> +            cpu_physical_memory_write_rom(rom->as ? rom->as :
>> +                                                    &address_space_memory,
>
> Should we just make rom->as be &address_space_memory if the caller
> doesn't provide one rather than having it be NULL and then special
> casing what NULL means? (This will also avoid potentially odd
> effects with some of the ROMs in the list having &address_space_memory
> for an explicitly specified AS and some having NULL for the same
> AS but implicitly specified, which is otherwise a pain to deal with
> in comparisons.)

Good point, I have added the setter in rom_insert() function.

Thanks,

Alistair

>
> thanks
> -- PMM
>