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[PATCH] x86: make CONFIG_HOTPLUG_CPU depend on !X86_PC

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Make CONFIG_HOTPLUG_CPU depend on !X86_PC, so we need to turn on either
CONFIG_GENERICARCH, CONFIG_BIGSMP or any other subarch except X86_PC when
CONFIG_HOTPLUG_CPU=y

With 2.6.15+ kernels when CONFIG_HOTPLUG_CPU is turned on we switch to
bigsmp mode for sending IPI's and ioapic configurations that caused the
following error message.

>> More than 8 CPUs detected and CONFIG_X86_PC cannot handle it.
>> Use CONFIG_X86_GENERICARCH or CONFIG_X86_BIGSMP.

Originally bigsmp was added just to handle >8 cpus, but now with hotplug
cpu support we need to use bigsmp mode (why?  see below), that cause the
above error message even if there were less than 8 cpus in the system.

The message is bogus, but we are cannot use logical flat mode due to issues
with broadcast IPI can confuse a CPU just comming up.  We use flat physical
mode just like x86_64 case.  More details on why bigsmp now uses flat
physical mode (vs.  cluster mode) in following link.

http://marc.theaimsgroup.com/?l=linux-kernel&m=113261865814107&w=2

Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Ashok Raj 2006-03-25 03:06:50 -08:00 committed by Linus Torvalds
parent f5335c0f1b
commit d3f4aaa3d7
1 changed files with 1 additions and 1 deletions
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arch/i386/Kconfig
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@ -737,7 +737,7 @@ config PHYSICAL_START
config HOTPLUG_CPU
bool "Support for hot-pluggable CPUs (EXPERIMENTAL)"
depends on SMP && HOTPLUG && EXPERIMENTAL && !X86_VOYAGER
depends on SMP && HOTPLUG && EXPERIMENTAL && !X86_VOYAGER && !X86_PC
---help---
Say Y here to experiment with turning CPUs off and on. CPUs
can be controlled through /sys/devices/system/cpu.