3 deleted 179 characters in body
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I think you may run into some memory area used by PCI/ACPI or some such hardware. There might be a memory mapped device that doesn't like being accessed. I can't tell what address exactly causes the problem, but it's usual for some special areas to be located just under the 4 GB limit.

On one machine with 4 GB memory, the kernel prints the following on boot:

BIOS-e820: 0000000000000000 - 000000000009e400 (usable)
BIOS-e820: 000000000009e400 - 00000000000a0000 (reserved)
BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 00000000cf690000 (usable)
BIOS-e820: 00000000cf690000 - 00000000cf6e0000 (reserved)
BIOS-e820: 00000000cf6e0000 - 00000000cf6e3000 (ACPI NVS)
BIOS-e820: 00000000cf6e3000 - 00000000cf6f0000 (ACPI data)
BIOS-e820: 00000000cf6f0000 - 00000000cf700000 (reserved)
BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved)
BIOS-e820: 0000000100000000 - 0000000130000000 (usable)

Part of the usable memory is above the 4 GB limit at 0x100000000 and there seems to be holes between 0xcf700000 and 0xfec00000.

The areas corresponding to "usable" memory are also shown in /proc/iomem, marked as "System RAM". (the file also contains information about the other memory areas.) You might be safer just reading from those areas.

$ grep "System RAM" /proc/iomem 
00001000-0009e3ff : System RAM
00100000-cf68ffff : System RAM
100000000-12fffffff : System RAM

I think you may run into some memory area used by PCI/ACPI or some such hardware. There might be a memory mapped device that doesn't like being accessed. I can't tell what address exactly causes the problem, but it's usual for some special areas to be located just under the 4 GB limit.

On one machine with 4 GB memory, the kernel prints the following on boot:

BIOS-e820: 0000000000000000 - 000000000009e400 (usable)
BIOS-e820: 000000000009e400 - 00000000000a0000 (reserved)
BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 00000000cf690000 (usable)
BIOS-e820: 00000000cf690000 - 00000000cf6e0000 (reserved)
BIOS-e820: 00000000cf6e0000 - 00000000cf6e3000 (ACPI NVS)
BIOS-e820: 00000000cf6e3000 - 00000000cf6f0000 (ACPI data)
BIOS-e820: 00000000cf6f0000 - 00000000cf700000 (reserved)
BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved)
BIOS-e820: 0000000100000000 - 0000000130000000 (usable)

The areas corresponding to "usable" memory are also shown in /proc/iomem, marked as "System RAM". (the file also contains information about the other memory areas.) You might be safer just reading from those areas.

$ grep "System RAM" /proc/iomem 
00001000-0009e3ff : System RAM
00100000-cf68ffff : System RAM
100000000-12fffffff : System RAM

I think you may run into some memory area used by PCI/ACPI or some such hardware. There might be a memory mapped device that doesn't like being accessed. I can't tell what address exactly causes the problem, but it's usual for some special areas to be located just under the 4 GB limit.

On one machine with 4 GB memory, the kernel prints the following on boot:

BIOS-e820: 0000000000000000 - 000000000009e400 (usable)
BIOS-e820: 000000000009e400 - 00000000000a0000 (reserved)
BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 00000000cf690000 (usable)
BIOS-e820: 00000000cf690000 - 00000000cf6e0000 (reserved)
BIOS-e820: 00000000cf6e0000 - 00000000cf6e3000 (ACPI NVS)
BIOS-e820: 00000000cf6e3000 - 00000000cf6f0000 (ACPI data)
BIOS-e820: 00000000cf6f0000 - 00000000cf700000 (reserved)
BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved)
BIOS-e820: 0000000100000000 - 0000000130000000 (usable)

Part of the usable memory is above the 4 GB limit at 0x100000000 and there seems to be holes between 0xcf700000 and 0xfec00000.

The areas corresponding to "usable" memory are also shown in /proc/iomem, marked as "System RAM". (the file also contains information about the other memory areas.) You might be safer just reading from those areas.

$ grep "System RAM" /proc/iomem 
00001000-0009e3ff : System RAM
00100000-cf68ffff : System RAM
100000000-12fffffff : System RAM
2 deleted 179 characters in body
source | link

I think you may run into some memory area used by PCI/ACPI or some such hardware. There might be a memory mapped device that doesn't like being accessed. I can't tell what address exactly causes the problem, but it's usual for some special areas to be located just under the 4 GB limit.

On one machine with 4 GB memory, the kernel prints the following on boot:

[    0.000000]  BIOS-e820: 0000000000000000 - 000000000009e400 (usable)
[    0.000000]  BIOS-e820: 000000000009e400 - 00000000000a0000 (reserved)
[    0.000000]  BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
[    0.000000]  BIOS-e820: 0000000000100000 - 00000000cf690000 (usable)
[    0.000000]  BIOS-e820: 00000000cf690000 - 00000000cf6e0000 (reserved)
[    0.000000]  BIOS-e820: 00000000cf6e0000 - 00000000cf6e3000 (ACPI NVS)
[    0.000000]  BIOS-e820: 00000000cf6e3000 - 00000000cf6f0000 (ACPI data)
[    0.000000]  BIOS-e820: 00000000cf6f0000 - 00000000cf700000 (reserved)
[    0.000000]  BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
[    0.000000]  BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved)
[    0.000000]  BIOS-e820: 0000000100000000 - 0000000130000000 (usable)

The areas corresponding to "usable" memory are also shown in /proc/iomem, marked as "System RAM". (the filesfile also contains information about the other memory areas.) You might be safer just reading from those areas.

$ grep "System RAM" /proc/iomem 
00001000-0009e3ff : System RAM
00100000-cf68ffff : System RAM
100000000-12fffffff : System RAM

I think you may run into some memory area used by PCI/ACPI or some such hardware. There might be a memory mapped device that doesn't like being accessed. I can't tell what address exactly causes the problem, but it's usual for some special areas to be located just under the 4 GB limit.

On one machine with 4 GB memory, the kernel prints the following on boot:

[    0.000000]  BIOS-e820: 0000000000000000 - 000000000009e400 (usable)
[    0.000000]  BIOS-e820: 000000000009e400 - 00000000000a0000 (reserved)
[    0.000000]  BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
[    0.000000]  BIOS-e820: 0000000000100000 - 00000000cf690000 (usable)
[    0.000000]  BIOS-e820: 00000000cf690000 - 00000000cf6e0000 (reserved)
[    0.000000]  BIOS-e820: 00000000cf6e0000 - 00000000cf6e3000 (ACPI NVS)
[    0.000000]  BIOS-e820: 00000000cf6e3000 - 00000000cf6f0000 (ACPI data)
[    0.000000]  BIOS-e820: 00000000cf6f0000 - 00000000cf700000 (reserved)
[    0.000000]  BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
[    0.000000]  BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved)
[    0.000000]  BIOS-e820: 0000000100000000 - 0000000130000000 (usable)

The areas corresponding to "usable" memory are also shown in /proc/iomem, marked as "System RAM". (the files also contains information about the other memory areas.) You might be safer just reading from those areas.

$ grep "System RAM" /proc/iomem 
00001000-0009e3ff : System RAM
00100000-cf68ffff : System RAM
100000000-12fffffff : System RAM

I think you may run into some memory area used by PCI/ACPI or some such hardware. There might be a memory mapped device that doesn't like being accessed. I can't tell what address exactly causes the problem, but it's usual for some special areas to be located just under the 4 GB limit.

On one machine with 4 GB memory, the kernel prints the following on boot:

BIOS-e820: 0000000000000000 - 000000000009e400 (usable)
BIOS-e820: 000000000009e400 - 00000000000a0000 (reserved)
BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 00000000cf690000 (usable)
BIOS-e820: 00000000cf690000 - 00000000cf6e0000 (reserved)
BIOS-e820: 00000000cf6e0000 - 00000000cf6e3000 (ACPI NVS)
BIOS-e820: 00000000cf6e3000 - 00000000cf6f0000 (ACPI data)
BIOS-e820: 00000000cf6f0000 - 00000000cf700000 (reserved)
BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved)
BIOS-e820: 0000000100000000 - 0000000130000000 (usable)

The areas corresponding to "usable" memory are also shown in /proc/iomem, marked as "System RAM". (the file also contains information about the other memory areas.) You might be safer just reading from those areas.

$ grep "System RAM" /proc/iomem 
00001000-0009e3ff : System RAM
00100000-cf68ffff : System RAM
100000000-12fffffff : System RAM
1
source | link

I think you may run into some memory area used by PCI/ACPI or some such hardware. There might be a memory mapped device that doesn't like being accessed. I can't tell what address exactly causes the problem, but it's usual for some special areas to be located just under the 4 GB limit.

On one machine with 4 GB memory, the kernel prints the following on boot:

[    0.000000]  BIOS-e820: 0000000000000000 - 000000000009e400 (usable)
[    0.000000]  BIOS-e820: 000000000009e400 - 00000000000a0000 (reserved)
[    0.000000]  BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
[    0.000000]  BIOS-e820: 0000000000100000 - 00000000cf690000 (usable)
[    0.000000]  BIOS-e820: 00000000cf690000 - 00000000cf6e0000 (reserved)
[    0.000000]  BIOS-e820: 00000000cf6e0000 - 00000000cf6e3000 (ACPI NVS)
[    0.000000]  BIOS-e820: 00000000cf6e3000 - 00000000cf6f0000 (ACPI data)
[    0.000000]  BIOS-e820: 00000000cf6f0000 - 00000000cf700000 (reserved)
[    0.000000]  BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
[    0.000000]  BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved)
[    0.000000]  BIOS-e820: 0000000100000000 - 0000000130000000 (usable)

The areas corresponding to "usable" memory are also shown in /proc/iomem, marked as "System RAM". (the files also contains information about the other memory areas.) You might be safer just reading from those areas.

$ grep "System RAM" /proc/iomem 
00001000-0009e3ff : System RAM
00100000-cf68ffff : System RAM
100000000-12fffffff : System RAM