Re: 2.6.27rc1 cannot boot more than 8CPUs

Yinghai Lu
2008-08-11T20:04:16Z

On Mon, Aug 11, 2008 at 12:59 PM, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Jeff Chua <jeff.chua.linux@gmail.com> wrote:
>
>> On Wed, Aug 6, 2008 at 2:42 PM, Jeff Chua <jeff.chua.linux@gmail.com> wrote:
>> > On Wed, Aug 6, 2008 at 2:01 PM, Linus Torvalds
>> > <torvalds@linux-foundation.org> wrote:
>> >> One trivial thing to try would be to just bisect it. I assume 2.6.26 is
>> > Bisecting now.
>>
>> Thanks to all the great helpful suggestions from everyone, and this
>> turns out that I just need to enable the following switches, so I
>> didn't bisect further, and since it's first machine that I've tried
>> with more than 8 CPUs so I wasn't sure whether 2.6.16 has the same
>> problem, but if you wish, I could give 2.6.16 a try.
>>
>> > CONFIG_X86_GENERICARCH=y
>> > CONFIG_X86_BIGSMP=y
>>
>> Thank you all for the great linux kernel!
>
> i still consider a silent boot hang a bug we need to fix.
>
> bigsmp might be required to have all cpus available on your box, but the
> kernel is still supposed to transparently fall back to less CPUs (and
> print a warning) if it cannot do that.
>
in setup.c::setup_arch() after go over with madt or mptable

#if defined(CONFIG_SMP) && defined(CONFIG_X86_PC) && defined(CONFIG_X86_32)
if (def_to_bigsmp)
printk(KERN_WARNING "More than 8 CPUs detected and "
"CONFIG_X86_PC cannot handle it.\nUse "
"CONFIG_X86_GENERICARCH or
CONFIG_X86_BIGSMP.\n"); ===> here need to change "or" to "and"
#endif

or just panic here? because screen scroll to pass it, and user will
not notice that...

YH