Re: [PATCH]Make gp value point to Region 5 in mca handler

Zou Nan hai
2006-09-14T00:25:15Z

On Wed, 2006-09-13 at 17:54, Keith Owens wrote:
> Zou Nan hai (on 13 Sep 2006 12:55:25 +0800) wrote:
> >MCA dispatch code take physical address of GP passed from SAL,
> >then call DATA_PA_TO_VA twice on GP before call into C code.
> >The first time is in ia64_set_kernel_register, the second time is in
> >VIRTUAL_MODE_ENTER.
> >The gp is changed to a virtual address in region 7 because DATA_PA_TO_VA
> >is implemented
> >by dep instruction.
> >
> >However when notify blocks were called from MCA handler code,
> >because notify blocks are supported by callback function pointers,
> >gp value value was switched to region 5 again.
> >
> >
> >The patch set gp register to kernel gp of region 5 at entry of MCA
> >dispatch.
> >
> >Signed-off-by: Zou Nan hai <nanhai.zou@intel.com>
>
> The idea is right, but there is no need to pass __gp to
> VIRTUAL_MODE_ENTER. There will never be a case of VIRTUAL_MODE_ENTER
> followed by entry to a module, so just hard code 'movl r1 = __gp' into
> VIRTUAL_MODE_ENTER and drop it from the parameter list.

OK, I felt a little weird to put hard code in a macro.., but I think it
does not matter much since the macro is only used 2 times.

the updated patch

Signed-off-by: Zou Nan hai <nanhai.zou@intel.com>

diff -Nraup linux-2.6.18-rc6/arch/ia64/kernel/mca_asm.S linux-2.6.18-rc6-fix/arch/ia64/kernel/mca_asm.S
--- linux-2.6.18-rc6/arch/ia64/kernel/mca_asm.S 2006-09-14 10:33:08.000000000 +0800
+++ linux-2.6.18-rc6-fix/arch/ia64/kernel/mca_asm.S 2006-09-14 10:35:49.000000000 +0800
@@ -1025,18 +1025,13 @@ ia64_old_stack:

ia64_set_kernel_registers:
add temp3=MCA_SP_OFFSET, r3
- add temp4=MCA_SOS_OFFSET+SOS(OS_GP), r3
mov b0=r2 // save return address
GET_IA64_MCA_DATA(temp1)
;;
- add temp4=temp4, temp1 // &struct ia64_sal_os_state.os_gp
add r12=temp1, temp3 // kernel stack pointer on MCA/INIT stack
add r13=temp1, r3 // set current to start of MCA/INIT stack
add r20=temp1, r3 // physical start of MCA/INIT stack
;;
- ld8 r1=[temp4] // OS GP from SAL OS state
- ;;
- DATA_PA_TO_VA(r1,temp1)
DATA_PA_TO_VA(r12,temp2)
DATA_PA_TO_VA(r13,temp3)
;;
diff -Nraup linux-2.6.18-rc6/include/asm-ia64/mca_asm.h linux-2.6.18-rc6-fix/include/asm-ia64/mca_asm.h
--- linux-2.6.18-rc6/include/asm-ia64/mca_asm.h 2006-06-18 09:49:35.000000000 +0800
+++ linux-2.6.18-rc6-fix/include/asm-ia64/mca_asm.h 2006-09-14 10:36:33.000000000 +0800
@@ -197,9 +197,9 @@
movl temp2 = start_addr; \
;; \
mov cr.iip = temp2; \
+ movl gp = __gp \
;; \
DATA_PA_TO_VA(sp, temp1); \
- DATA_PA_TO_VA(gp, temp2); \
srlz.i; \
;; \
nop 1; \