Re: [Qemu-devel] [PATCH 02/23] bsd-user: add initial support for mips/mips64

[Stacey Son]

On Jun 24, 2013, at 12:15 PM, Peter Maydell wrote:

>> 
>> +#if defined(TARGET_MIPS)
>> +
>> +/* Compare to sys/mips/mips/trap.c */
>> +
>> +void cpu_loop(CPUMIPSState *env)
> 
> I suspect you'd do better in the long term to restructure
> to pull cpu_loop out into a per-architecture source file
> and avoid the ifdefs. (This is something I'd like to do to
> the linux-user/ code, which is currently even more ifdef-ridden
> than bsd-user/.)


Yes, the cpu_loop()'s and the cpu initialization code is actually separated out 
in the arm arch patch for all the arch's.

> 
>> --- a/target-mips/mips-defs.h
>> +++ b/target-mips/mips-defs.h
>> @@ -10,8 +10,17 @@
>> 
>> #if defined(TARGET_MIPS64)
>> #define TARGET_LONG_BITS 64
>> -#define TARGET_PHYS_ADDR_SPACE_BITS 36
>> -#define TARGET_VIRT_ADDR_SPACE_BITS 42
>> +#  if defined(CONFIG_BSD) && defined(CONFIG_USER_ONLY)
>> +#    define TARGET_PHYS_ADDR_SPACE_BITS 59
>> +#    ifdef TARGET_ABI32
>> +#       define TARGET_VIRT_ADDR_SPACE_BITS 32
>> +#    else
>> +#       define TARGET_VIRT_ADDR_SPACE_BITS 62
>> +#    endif
>> +#  else
>> +#    define TARGET_PHYS_ADDR_SPACE_BITS 36
>> +#    define TARGET_VIRT_ADDR_SPACE_BITS 42
>> +#  endif
>> #else
>> #define TARGET_LONG_BITS 32
>> #define TARGET_PHYS_ADDR_SPACE_BITS 36
> 
> This looks a little fishy -- could you give some rationale?
> Why does only BSD need to do this? Why do you need to
> change the TARGET_PHYS_ADDR_SPACE_BITS for a -user target?
> Where do the numbers come from?


If I remember correctly these:

>> +#  if defined(CONFIG_BSD) && defined(CONFIG_USER_ONLY)
>> +#    define TARGET_PHYS_ADDR_SPACE_BITS 59
>> +#    ifdef TARGET_ABI32
>> +#       define TARGET_VIRT_ADDR_SPACE_BITS 32
>> +#    else
>> +#       define TARGET_VIRT_ADDR_SPACE_BITS 62
>> +#    endif

come from the See Mips Run book.

The reason they were changed for the bsd-user is FreeBSD puts the text segment 
in something like 0x12000000 (plus or minus a zero) and the stack at 
0x8000000000 (- minus a page or two) for mips64 which didn't work as defined 
originally.

-stacey.