Re: More than 8 CPUs detected and CONFIG_X86_PC cannot handle it on2.6.16-rc6

[Andrew Morton]

Ashok Raj <ashok.raj@xxxxxxxxx> wrote:
>
> When CONFIG_HOTPLUG_CPU is turned on we always use physflat mode (bigsmp) even 
>  when #of CPUs are less than 8 to avoid sending IPI to offline processors.
> 
>  Without having BIGSMP on it spits out a warning during boot on systems that
>  seems misleading, since it complains even on systems that have less
>  than 8 cpus.
> 
> ...
>
>  --- linux-2.6.16-rc6-mm1.orig/arch/i386/Kconfig
>  +++ linux-2.6.16-rc6-mm1/arch/i386/Kconfig
>  @@ -760,7 +760,7 @@ 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_GENERICARCH || X86_BIGSMP)
>   	---help---
>   	  Say Y here to experiment with turning CPUs off and on.  CPUs
>   	  can be controlled through /sys/devices/system/cpu.

One of the main reasons for turning on CONFIG_HOTPLUG_CPU on x86 is
actually for suspend-to-disk on SMP.  I don't think it's desirable to force
all those little machines to use X86_GENERICARCH || X86_BIGSMP.  And it'd
be good to make that warning go away for 2.6.16.
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