Kernel configuration influence on local APIC

Kernel configuration influence on local APIC

[Marc Haber]

Hi,

I have a system that needs the "lapic" option on the kernel command
line when I run the system with the 2.6.35.4 kernel that I use on most
of my servers. However, when I use grml as a rescue system on the box,
the system runs fine without this kernel command line.

The daily grml image that I have been trying is from last week and
uses a 2.6.35.4 image as well. The grml system has
[    0.000000] ACPI: LAPIC (acpi_id[0x01] lapic_id[0x00] enabled)
[    0.000000] ACPI: LAPIC (acpi_id[0x02] lapic_id[0x02] enabled)
[    0.000000] ACPI: LAPIC (acpi_id[0x03] lapic_id[0x04] enabled)
[    0.000000] ACPI: LAPIC (acpi_id[0x04] lapic_id[0x06] enabled)
[    0.000000] ACPI: LAPIC (acpi_id[0x05] lapic_id[0x84] disabled)
[    0.000000] ACPI: LAPIC (acpi_id[0x06] lapic_id[0x85] disabled)
[    0.000000] ACPI: LAPIC (acpi_id[0x07] lapic_id[0x86] disabled)
[    0.000000] ACPI: LAPIC (acpi_id[0x08] lapic_id[0x87] disabled)
[    0.000000] ACPI: LAPIC_NMI (acpi_id[0xff] dfl dfl lint[0x1])
in its dmesg, but CONFIG_X86_LOCAL_APIC=y is set - does that mean that
the lapic is disabled on grml?

What do I lose when I run the server without the lapic, and which
kernel setting should I play with to get the productive kernel to work
with the lapic enabled?

Greetings
Marc

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