Re: [Fastboot] [PATCH]IA64 kexec/kdump patch for INIT

[Keith Owens <kaos@sgi.com>]

Takao Indoh (on Thu, 07 Sep 2006 23:48:51 +0900) wrote:
>On Thu, 7 Sep 2006 21:01:17 +0800, "Yu, Luming" wrote:
>
>>>>Did  saved Os gp in SAL OS state  somehow get overridden before 
>>>>ia64_set_kernel_registers prior to invocation of ia64_init_handler?
>>>>
>>>>I assume the following code (in ia64_set_kernel_registers ) 
>>>should restore 
>>>>correct GP value.
>>>>
>>>>ia64_set_kernel_registers:
>>>>	...
>>>>        ;;
>>>>        ld8 r1=[temp4]          // OS GP from SAL OS state
>>>
>>>Yes, but this gp value is physical address.
>>>In the next line, gp is changed to virtual address.
>>>
>>>DATA_PA_TO_VA(r1,temp1)
>>>
>>>This macro just sets region7 bit, so gp value becomes region7 address.
>>
>>Ok, could you please confirm what is the value of r1 before
>>DATA_PA_TO_VA(r1, temp1)?
>>I guess we need to set r1 = __gp in ia64_set_kernel_registers.
>>If not,  this is a bug.  Am I right?
>
>In the ia64_mca_init, the value of ia64_tpa(ia64_getreg(_IA64_REG_GP)
>is registered as gp value. When cpu comes into the above code, r1 is set
>to this value, I think. Therefore, r1 has physical address of __gp
>before DATA_PA_TO_VA(r1, temp1). How do you think?
>
>I think you are right, I also think r1 has to be set to __gp before 
>calling ia64_init_handler.

It already is set in mca_asm.S.  Remember that ia64_init_handler is by
definition part of the kernel, it cannot be a module.  Therefore before
entering ia64_init_handler, r1 must be set to what the kernel expects
to be in r1.  The standard kernel's r1 is a region 7 address, not a
region 5 address.  The kernel (including __gp) is compiled as region 5
but relocated to region 7 during kernel load.

Is the kexec kernel running in region 5?  That may be where the
confusion is coming from.