Re: [Crash-utility] ARM support for CONFIG_SPARSEMEM: (was Re: DDimage)
Thanks Dave, MW, Jan,
I tried the patch which set machdep->section_size_bits and
machdep->max_physmem_bits.
When _SECTION_SIZE_BITS is 28, I got the following error, and failed in sparse_mem_init()
PAGESIZE=4096
mem_section_size = 0
NR_SECTION_ROOTS = 0
NR_MEM_SECTIONS = 16
SECTIONS_PER_ROOT = 512
SECTION_ROOT_MASK = 0x1ff
PAGES_PER_SECTION = 65536
crash: invalid size request: 0 type: "memory section root table"
And when _SECTION_SIZE_BITS is 22, I got the following and sparse_mem_init() returns with
out error.
PAGESIZE=4096
mem_section_size = 8
NR_SECTION_ROOTS = 2
NR_MEM_SECTIONS = 1024
SECTIONS_PER_ROOT = 512
SECTION_ROOT_MASK = 0x1ff
PAGES_PER_SECTION = 1024
... But I got another error later, which I will report later.
In memory.c:sparse_mem_init(),
vt->mem_sec is malloced as mem_section_size bytes block and readmem is called.
I suppose the mem_section_size should not be zero. I do not know _SECTION_SIZE_BITS 22 is
correct or not,
but the following caliculation of NR_SECTION_ROOTS() looks suspicious to me.
#define NR_SECTION_ROOTS() (NR_MEM_SECTIONS() / SECTIONS_PER_ROOT())
Something like (((NR_MEM_SECTIONS() - 1)/ SECTIONS_PER_ROOT()) + 1) ?
Best Regard,
Takuo
[ dropped my Nokia address from the CC list, since I'm not working
for Nokia
anymore ]
On Tue, May 24, 2011 at 09:58:48AM -0400, Dave Anderson wrote:
>
> BTW, I await any patches from the ARM folks to set these bits
> appropriately. Currently there is this for ARM in defs.h:
>
> #ifdef ARM
> ... [ cut ] ...
>
> #define _SECTION_SIZE_BITS 28
> #define _MAX_PHYSMEM_BITS 32
>
> #endif /* ARM */
>
> Yet you state above that you're using 22 for _SECTION_SIZE_BITS.
This varies between different SoCs and it is not used by others. Since it is
not stored in a crashdump IIRC, we really cannot set that value dynamically.
So I see two options:
1) leave it as is and make crash to complain when it detects such
situation or
2) guess the values and try to do the right thing (TM)
My preference goes with 2) provided that we can get it working on majority of
the ARM SoCs.
We could try to stick with _SECTION_SIZE_BITS=28, as it seems to be largest
currently used section size amongst different ARM SoCs, and hope that it works
with others where this is smaller.
Jan, Takuo: maybe you could try whether following patch works? I don't have
any hardware which use SPARSEMEM so I'm unable to test it.
Regards,
MW
diff --git a/arm.c b/arm.c
index 0347166..9d4afcc 100644
--- a/arm.c
+++ b/arm.c
@@ -260,6 +260,9 @@ arm_init(int when)
STRUCT_EXISTS("pteval_t"))
machdep->flags |= PGTABLE_V2;
+ machdep->section_size_bits = _SECTION_SIZE_BITS;
+ machdep->max_physmem_bits = _MAX_PHYSMEM_BITS;
+
if (symbol_exists("irq_desc"))
ARRAY_LENGTH_INIT(machdep->nr_irqs, irq_desc,
"irq_desc", NULL, 0);
--
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