x86_64: restore the proper NR_IRQS define so larger systems work.
As pointed out and tracked by Yinghai Lu <yhlu.kernel@gmail.com>: Dhaval Giani got: kernel BUG at arch/x86/kernel/io_apic_64.c:357! invalid opcode: 0000 [1] SMP CPU 24 ... his system (x3950) has 8 ioapic, irq > 256 This was caused by: commit 9b7dc567 Author: Thomas Gleixner <tglx@linutronix.de> Date: Fri May 2 20:10:09 2008 +0200 x86: unify interrupt vector defines The interrupt vector defines are copied 4 times around with minimal differences. Move them all into asm-x86/irq_vectors.h It appears that Thomas did not notice that x86_64 does something completely different when he merge irq_vectors.h We can solve this for 2.6.27 by simply reintroducing the old heuristic for setting NR_IRQS on x86_64 to a usable value, which trivially removes the regression. Long term it would be nice to harmonize the handling of ioapic interrupts of x86_32 and x86_64 so we don't have this kind of confusion. Dhaval Giani <dhaval@linux.vnet.ibm.com> tested an earlier version of this patch by YH which confirms simply increasing NR_IRQS fixes the problem. Signed-off-by: NEric W. Biederman <ebiederm@xmission.com> Acked-by: NYinghai Lu <yhlu.kernel@gmail.com> Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com> Cc: Mike Travis <travis@sgi.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: NIngo Molnar <mingo@elte.hu>
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