----- Original Message -----
> Hello Dave and Mahesh,
>
> We also tried to solve the problem and came up with an alternative
> solution.
>
> The function s390x_max_physmem_bits() solves the following equation:
>
> array_len == NR_MEM_SECTIONS / SECTIONS_PER_ROOT
>
> 2^(MAX_PYSMEM_BITS - SECTION_SIZE_BITS)
> ---------------------------------------
> == PAGE_SIZE
> -------------------------
> sizeof(struct mem_section)
>
> This leads to the following:
>
> MAX_PYSMEM_BITS == SECTION_SIZE_BITS + log2(array_len) +
> log2(PAGE_SIZE)
> - log2(sizeof(struct mem_section));
>
> I tested the patch with 42 and 46 bits and for both it seems to work.
> I will leave now for vacation and will return January the 9th 2012.
>
> I leave it to you which solution to take.
No -- I leave to you guys to decide. I appreciate the simplicity of
your solution, but Mahesh's patch is easier to understand.
So please decide before you go home -- I was hoping to get a release
out today!
> Merry Christmas!
>
> Michael
>
> PS: I think this patch also fixes a bug in verify_ptn()...
> BTOP vs. PTOB :-)
Hey, you're right!
Dave
> ---
> kernel.c | 2 +-
> memory.c | 2 +-
> s390x.c | 17 ++++++++++++++++-
> 3 files changed, 18 insertions(+), 3 deletions(-)
>
> --- a/kernel.c
> +++ b/kernel.c
> @@ -275,7 +275,7 @@ kernel_init()
> MEMBER_OFFSET_INIT(prio_array_nr_active, "prio_array",
> "nr_active");
> STRUCT_SIZE_INIT(runqueue, rqstruct);
> STRUCT_SIZE_INIT(prio_array, "prio_array");
> -
> + STRUCT_SIZE_INIT(mem_section, "mem_section");
> MEMBER_OFFSET_INIT(rq_cfs, "rq", "cfs");
>
> /*
> --- a/memory.c
> +++ b/memory.c
> @@ -13601,7 +13601,7 @@ verify_pfn(ulong pfn)
> for (i = machdep->max_physmem_bits; i < machdep->bits; i++)
> mask |= ((physaddr_t)1 << i);
>
> - if (mask & BTOP(pfn))
> + if (mask & PTOB(pfn))
> return FALSE;
>
> return TRUE;
> --- a/s390x.c
> +++ b/s390x.c
> @@ -17,6 +17,7 @@
> */
> #ifdef S390X
> #include <elf.h>
> +#include <math.h>
> #include "defs.h"
> #include "netdump.h"
>
> @@ -283,6 +284,19 @@ static void s390x_process_elf_notes(void
> }
>
> /*
> + * The older s390x kernels use _MAX_PHYSMEM_BITS as 42 and the
> + * newer kernels use 46 bits. This function calculates the bits
> + * via a generic function.
> + */
> +static int s390x_max_physmem_bits(void)
> +{
> + unsigned long array_len = get_array_length("mem_section", NULL, 0);
> +
> + return _SECTION_SIZE_BITS + log2(array_len) + 12 /* log2(PAGE_SIZE)
> */
> + - log2(SIZE(mem_section));
> +}
> +
> +/*
> * Do all necessary machine-specific setup here. This is called
> several
> * times during initialization.
> */
> @@ -350,13 +364,14 @@ s390x_init(int when)
> if (!machdep->hz)
> machdep->hz = HZ;
> machdep->section_size_bits = _SECTION_SIZE_BITS;
> - machdep->max_physmem_bits = _MAX_PHYSMEM_BITS;
> + machdep->max_physmem_bits = s390x_max_physmem_bits();
> s390x_offsets_init();
> break;
>
> case POST_INIT:
> break;
> }
> + fprintf(stderr, "XXX %d\n", machdep->max_physmem_bits);
> }
>
> /*
>
>
