Michael Holzheu wrote:
Hi Dave,
When starting crash on s390(x) with CONFIG_SPARSEMEM enabled we get the
following error message:
crash: CONFIG_SPARSEMEM kernels not supported for this architecture
The following patch fixes this problem, but I am not sure, if I set
_MAX_PHYSMEM_BITS to the correct value (I used 31 for s390 and 64 for
s390x). Could you please explain the meaning of _MAX_PHSYSMEM_BITS?
---
Hi Michael,
Actually, the originator of CONFIG_SPARSEMENT support is your IBM compatriot,
and can probably answer this best:
4.0-2.22 - Incorporated initial patch-set to implement support for kernels built
with CONFIG_SPARSEMEM. (dwilder@xxxxxxxxxx)
...
Dave is still listed as a member of this mailing list.
Anyway, as I understand it, the _MAX_PHYSMEM_BITS() macro for each architecture
is a clone of the kernel's per-arch MAX_PHYSMEM_BITS #define. For the s390
arch, it's found in "include/asm-s390/sparsemem.h":
#ifndef _ASM_S390_SPARSEMEM_H
#define _ASM_S390_SPARSEMEM_H
#define SECTION_SIZE_BITS 25
#ifdef CONFIG_64BIT
#define MAX_PHYSADDR_BITS 42
#define MAX_PHYSMEM_BITS 42
#else
#define MAX_PHYSADDR_BITS 31
#define MAX_PHYSMEM_BITS 31
#endif /* CONFIG_64BIT */
#endif /* _ASM_S390_SPARSEMEM_H */
And it -- along with SECTION_SIZE_BITS -- fits into the math for the SECTIONS_SHIFT value
in "include/linux/mmzone.h":
SECTIONS_SHIFT 839 #define SECTIONS_SHIFT (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS)
And so the crash utility follows its lead:
#define SECTION_SIZE_BITS() (machdep->section_size_bits)
#define MAX_PHYSMEM_BITS() (machdep->max_physmem_bits)
#define SECTIONS_SHIFT() (MAX_PHYSMEM_BITS() - SECTION_SIZE_BITS())
and also using the arch-specific SECTION_SIZE_BITS() in the same manner.
So I'm surprised that your patch "works"? It would seem that it would need to:
(1) to use "42" for the s390x _MAX_PHYSMEM_BITS, and
(2) you would also need to #define a _SECTION_SIZE_BITS value for the two
architectures as well.
Dave
diff -Naurp crash-4.0-6.3/defs.h crash-4.0-6.3-config-sparse/defs.h
--- crash-4.0-6.3/defs.h 2008-04-29 19:39:17.000000000 +0200
+++ crash-4.0-6.3-config-sparse/defs.h 2008-08-12 17:03:54.000000000 +0200
@@ -2634,6 +2634,8 @@ struct efi_memory_desc_t {
#define TIF_SIGPENDING (2)
+#define _MAX_PHYSMEM_BITS 31
+
#endif /* S390 */
#ifdef S390X
@@ -2656,6 +2658,8 @@ struct efi_memory_desc_t {
#define TIF_SIGPENDING (2)
+#define _MAX_PHYSMEM_BITS 64
+
#endif /* S390X */
#ifdef PLATFORM
diff -Naurp crash-4.0-6.3/s390.c crash-4.0-6.3-config-sparse/s390.c
--- crash-4.0-6.3/s390.c 2008-04-29 19:39:17.000000000 +0200
+++ crash-4.0-6.3-config-sparse/s390.c 2008-08-12 17:04:03.000000000 +0200
@@ -130,6 +130,7 @@ s390_init(int when)
machdep->dump_irq = s390_dump_irq;
if (!machdep->hz)
machdep->hz = HZ;
+ machdep->max_physmem_bits = _MAX_PHYSMEM_BITS;
break;
case POST_INIT:
diff -Naurp crash-4.0-6.3/s390x.c crash-4.0-6.3-config-sparse/s390x.c
--- crash-4.0-6.3/s390x.c 2008-04-29 19:39:16.000000000 +0200
+++ crash-4.0-6.3-config-sparse/s390x.c 2008-08-12 17:04:01.000000000 +0200
@@ -128,6 +128,7 @@ s390x_init(int when)
machdep->dump_irq = s390x_dump_irq;
if (!machdep->hz)
machdep->hz = HZ;
+ machdep->max_physmem_bits = _MAX_PHYSMEM_BITS;
break;
case POST_INIT:
--
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