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    SubjectReading /dev/mem by dd
    Hello everyone!

    I've found strange behavior of reading /dev/mem:

    for i in 0 1 2; do
    echo $i
    dd if=/dev/mem of=/dev/null skip=$((6+$i)) bs=$((0x20000000)) count=1
    done

    On some systems with Supermicro X8DTU I've got several messages during
    first 512Mb starting from 0xc000_0000:

    "BUG: soft lockup - CPU#xx stuck for 61s!"

    On other systems with the sameboard I've stuck without any errors at
    last 10Mb before 0x1_0000_0000. Local APIC access?

    On E5440 (Dell PowerEdge 1950) I've just got several:
    APIC error on CPU3: 00(80)
    APIC error on CPU3: 80(80)
    ...
    APIC error on CPU3: 80(80)
    That looks like wrong register access.

    [E5530] $ cat /proc/iomem
    00000000-0000ffff : reserved
    00010000-0009dbff : System RAM
    0009dc00-0009ffff : reserved
    000c0000-000cffff : pnp 00:0e
    000e0000-000fffff : reserved
    00100000-bf77ffff : System RAM
    00200000-006a37de : Kernel code
    006a37df-0091a57f : Kernel data
    00a68000-00b7cbaf : Kernel bss
    bf78e000-bf78ffff : reserved
    bf790000-bf79dfff : ACPI Tables
    bf79e000-bf7cffff : ACPI Non-volatile Storage
    bf7d0000-bf7dffff : reserved
    bf7ec000-bfffffff : reserved
    e0000000-efffffff : PCI MMCONFIG 0
    e0000000-efffffff : reserved
    e0000000-efffffff : pnp 00:0d
    f9000000-f9ffffff : PCI Bus 0000:07
    f9000000-f9ffffff : 0000:07:01.0
    faeda000-faeda0ff : 0000:00:1f.3
    faedc000-faedc3ff : 0000:00:1d.7
    faedc000-faedc3ff : ehci_hcd
    faede000-faede3ff : 0000:00:1a.7
    faede000-faede3ff : ehci_hcd
    faee0000-faee3fff : 0000:00:16.7
    faee4000-faee7fff : 0000:00:16.6
    faee8000-faeebfff : 0000:00:16.5
    faeec000-faeeffff : 0000:00:16.4
    faef0000-faef3fff : 0000:00:16.3
    faef4000-faef7fff : 0000:00:16.2
    faef8000-faefbfff : 0000:00:16.1
    faefc000-faefffff : 0000:00:16.0
    faf00000-faffffff : PCI Bus 0000:01
    faf00000-faf1ffff : 0000:01:00.1
    faf3c000-faf3ffff : 0000:01:00.1
    faf3c000-faf3ffff : igb
    faf40000-faf5ffff : 0000:01:00.1
    faf40000-faf5ffff : igb
    faf60000-faf7ffff : 0000:01:00.1
    faf60000-faf7ffff : igb
    faf80000-faf9ffff : 0000:01:00.0
    fafbc000-fafbffff : 0000:01:00.0
    fafbc000-fafbffff : igb
    fafc0000-fafdffff : 0000:01:00.0
    fafc0000-fafdffff : igb
    fafe0000-faffffff : 0000:01:00.0
    fafe0000-faffffff : igb
    fb000000-fbefffff : PCI Bus 0000:07
    fb000000-fb7fffff : 0000:07:01.0
    fbefc000-fbefffff : 0000:07:01.0
    fec00000-fec00fff : IOAPIC 0
    fec00000-fec00fff : pnp 00:0c
    fed00000-fed003ff : HPET 0
    fed1c000-fed1ffff : pnp 00:01
    fed1c000-fed1ffff : pnp 00:0a
    fed20000-fed3ffff : pnp 00:0a
    fed40000-fed8ffff : pnp 00:0a
    fee00000-fee00fff : Local APIC
    fee00000-fee00fff : reserved
    fee00000-fee00fff : pnp 00:0c
    ffc00000-ffffffff : reserved
    100000000-13fffffff : System RAM

    [ 0.000000] BIOS-provided physical RAM map:
    [ 0.000000] BIOS-e820: 0000000000000000 - 000000000009dc00 (usable)
    [ 0.000000] BIOS-e820: 000000000009dc00 - 00000000000a0000 (reserved)
    [ 0.000000] BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
    [ 0.000000] BIOS-e820: 0000000000100000 - 00000000bf780000 (usable)
    [ 0.000000] BIOS-e820: 00000000bf78e000 - 00000000bf790000 type 9
    [ 0.000000] BIOS-e820: 00000000bf790000 - 00000000bf79e000 (ACPI data)
    [ 0.000000] BIOS-e820: 00000000bf79e000 - 00000000bf7d0000 (ACPI NVS)
    [ 0.000000] BIOS-e820: 00000000bf7d0000 - 00000000bf7e0000 (reserved)
    [ 0.000000] BIOS-e820: 00000000bf7ec000 - 00000000c0000000 (reserved)
    [ 0.000000] BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
    [ 0.000000] BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
    [ 0.000000] BIOS-e820: 00000000ffc00000 - 0000000100000000 (reserved)
    [ 0.000000] BIOS-e820: 0000000100000000 - 0000000140000000 (usable)

    [E5440] $ cat /proc/iomem
    00000000-0009ffff : System RAM
    00000000-00000000 : Crash kernel
    000a0000-000bffff : Video RAM area
    000c0000-000c7fff : Video ROM
    000c9000-000c9fff : Adapter ROM
    000ca000-000cfbff : Adapter ROM
    000d0000-000d1dff : Adapter ROM
    000d2000-000d71ff : Adapter ROM
    000f0000-000fffff : System ROM
    00100000-bfb4ffff : System RAM
    00200000-003e1fbc : Kernel code
    003e1fbd-004bafe7 : Kernel data
    bfb50000-bfb65fff : reserved
    bfb66000-bfb85bff : ACPI Tables
    bfb85c00-bfffffff : reserved
    d0000000-d7ffffff : PCI Bus #10
    d0000000-d7ffffff : 0000:10:0d.0
    d8000000-d80fffff : PCI Bus #0c
    d8000000-d80fffff : PCI Bus #0d
    d80f0000-d80fffff : 0000:0d:0e.0
    d80f0000-d80fffff : megasas: LSI Logic
    e0000000-efffffff : reserved
    f2000000-f7ffffff : PCI Bus #04
    f4000000-f7ffffff : PCI Bus #05
    f4000000-f7ffffff : PCI Bus #06
    f4000000-f7ffffff : PCI Bus #07
    f4000000-f5ffffff : 0000:07:00.0
    f4000000-f5ffffff : bnx2
    f8000000-fbffffff : PCI Bus #02
    f8000000-fbffffff : PCI Bus #03
    f8000000-f9ffffff : 0000:03:00.0
    f8000000-f9ffffff : bnx2
    fc100000-fc2fffff : PCI Bus #10
    fc100000-fc11ffff : 0000:10:0d.0
    fc2d0000-fc2dffff : 0000:10:0d.0
    fc300000-fc5fffff : PCI Bus #0c
    fc400000-fc5fffff : PCI Bus #0d
    fc400000-fc407fff : 0000:0d:0e.0
    fc5c0000-fc5dffff : 0000:0d:0e.0
    fc5c0000-fc5dffff : megasas: LSI Logic
    fc600000-fc8fffff : PCI Bus #01
    fc7e0000-fc7effff : 0000:01:00.0
    fc7fc000-fc7fffff : 0000:01:00.0
    fc800000-fc8fffff : 0000:01:00.0
    fc900000-fc9003ff : 0000:00:1d.7
    fc900000-fc9003ff : ehci_hcd
    fe000000-ffffffff : reserved
    100000000-43fffffff : System RAM

    HP - ProLiant DL160G6 says:
    http://www.pixsup.com/uploads/7134cd3e33.png

    Rgds,
    Anton


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