Re: kdump broken on Altix 350

[Jay Lan <jlan@sgi.com>]

Luck, Tony wrote:
> Does this make kexec/kdump happier?  Bare minimum testing so far
> (builds and boots on tiger ... didn't try kexec yet).

Hi Tony,

Yep, the 2.6.27-rc7 kdump kernel built with this patch worked fine!

Actually you probably can predict the results by doing 'readelf -l
vmlinux'. If the PT_LOAD headers do not have a gap betweens headers,
it is good. In other words, if the (PhysAddr+MemSiz) rounded up to
Align value of one header is the same as the PhysAddr of the next
header, kexec should produce a good boot memmap for the kdump kernel.


Thanks for the patch!

jay

> 
> 
> 
> [IA64] Put the space for cpu0 per-cpu area into .data section
> 
> Initial fix for making sure that we can access percpu variables
> in all C code commit: 10617bbe84628eb18ab5f723d3ba35005adde143
> inadvertantly allocated the memory in the "percpu" section of
> the vmlinux ELF executable.  This confused kexec.
> 
> Signed-off-by: Tony Luck <tony.luck@intel.com>
> 
> diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
> index f667998..1a873b3 100644
> --- a/arch/ia64/include/asm/sections.h
> +++ b/arch/ia64/include/asm/sections.h
> @@ -11,6 +11,9 @@
>  #include <asm-generic/sections.h>
>  
>  extern char __per_cpu_start[], __per_cpu_end[], __phys_per_cpu_start[];
> +#ifdef	CONFIG_SMP
> +extern char __cpu0_per_cpu[];
> +#endif
>  extern char __start___vtop_patchlist[], __end___vtop_patchlist[];
>  extern char __start___rse_patchlist[], __end___rse_patchlist[];
>  extern char __start___mckinley_e9_bundles[], __end___mckinley_e9_bundles[];
> diff --git a/arch/ia64/kernel/head.S b/arch/ia64/kernel/head.S
> index 8bdea8e..66e491d 100644
> --- a/arch/ia64/kernel/head.S
> +++ b/arch/ia64/kernel/head.S
> @@ -367,16 +367,17 @@ start_ap:
>  	;;
>  #else
>  (isAP)	br.few 2f
> -	mov r20=r19
> -	sub r19=r19,r18
> +	movl r20=__cpu0_per_cpu
>  	;;
>  	shr.u r18=r18,3
>  1:
> -	ld8 r21=[r20],8;;
> -	st8[r19]=r21,8
> +	ld8 r21=[r19],8;;
> +	st8[r20]=r21,8
>  	adds r18=-1,r18;;
>  	cmp4.lt p7,p6=0,r18
>  (p7)	br.cond.dptk.few 1b
> +	mov r19=r20
> +	;;
>  2:
>  #endif
>  	tpa r19=r19
> diff --git a/arch/ia64/kernel/vmlinux.lds.S b/arch/ia64/kernel/vmlinux.lds.S
> index de71da8..10a7d47 100644
> --- a/arch/ia64/kernel/vmlinux.lds.S
> +++ b/arch/ia64/kernel/vmlinux.lds.S
> @@ -215,9 +215,6 @@ SECTIONS
>    /* Per-cpu data: */
>    percpu : { } :percpu
>    . = ALIGN(PERCPU_PAGE_SIZE);
> -#ifdef	CONFIG_SMP
> -  . = . + PERCPU_PAGE_SIZE;	/* cpu0 per-cpu space */
> -#endif
>    __phys_per_cpu_start = .;
>    .data.percpu PERCPU_ADDR : AT(__phys_per_cpu_start - LOAD_OFFSET)
>  	{
> @@ -233,6 +230,11 @@ SECTIONS
>    data : { } :data
>    .data : AT(ADDR(.data) - LOAD_OFFSET)
>  	{
> +#ifdef	CONFIG_SMP
> +  . = ALIGN(PERCPU_PAGE_SIZE);
> +		__cpu0_per_cpu = .;
> +  . = . + PERCPU_PAGE_SIZE;	/* cpu0 per-cpu space */
> +#endif
>  		DATA_DATA
>  		*(.data1)
>  		*(.gnu.linkonce.d*)
> diff --git a/arch/ia64/mm/contig.c b/arch/ia64/mm/contig.c
> index e566ff4..0ee085e 100644
> --- a/arch/ia64/mm/contig.c
> +++ b/arch/ia64/mm/contig.c
> @@ -163,7 +163,7 @@ per_cpu_init (void)
>  	 * get_zeroed_page().
>  	 */
>  	if (first_time) {
> -		void *cpu0_data = __phys_per_cpu_start - PERCPU_PAGE_SIZE;
> +		void *cpu0_data = __cpu0_per_cpu;
>  
>  		first_time=0;
>  
> diff --git a/arch/ia64/mm/discontig.c b/arch/ia64/mm/discontig.c
> index 78026aa..d8c5fcd 100644
> --- a/arch/ia64/mm/discontig.c
> +++ b/arch/ia64/mm/discontig.c
> @@ -144,7 +144,7 @@ static void *per_cpu_node_setup(void *cpu_data, int node)
>  
>  	for_each_possible_early_cpu(cpu) {
>  		if (cpu == 0) {
> -			void *cpu0_data = __phys_per_cpu_start - PERCPU_PAGE_SIZE;
> +			void *cpu0_data = __cpu0_per_cpu;
>  			__per_cpu_offset[cpu] = (char*)cpu0_data -
>  				__per_cpu_start;
>  		} else if (node == node_cpuid[cpu].nid) {
> --
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