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    SubjectRe: [PATCH] x86_64: Restore the proper NR_IRQS define so larger systems work.
    Yinghai Lu wrote:
    > On Sat, Aug 2, 2008 at 10:26 PM, Eric W. Biederman
    > <ebiederm@xmission.com> wrote:
    >
    >> 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 9b7dc567d03d74a1fbae84e88949b6a60d922d82
    >> 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: Eric W. Biederman <ebiederm@xmission.com>
    >> ---
    >> include/asm-x86/irq_vectors.h | 10 +++++++++-
    >> 1 files changed, 9 insertions(+), 1 deletions(-)
    >>
    >> diff --git a/include/asm-x86/irq_vectors.h b/include/asm-x86/irq_vectors.h
    >> index 90b1d1f..a13eb6c 100644
    >> --- a/include/asm-x86/irq_vectors.h
    >> +++ b/include/asm-x86/irq_vectors.h
    >> @@ -109,7 +109,15 @@
    >> #define LAST_VM86_IRQ 15
    >> #define invalid_vm86_irq(irq) ((irq) < 3 || (irq) > 15)
    >>
    >> -#if !defined(CONFIG_X86_VOYAGER)
    >> +#ifdef CONFIG_X86_64
    >> +# if NR_CPUS < MAX_IO_APICS
    >> +# define NR_IRQS (NR_VECTORS + (32 * NR_CPUS))
    >> +# else
    >> +# define NR_IRQS (NR_VECTORS + (32 * MAX_IO_APICS ))
    >> +# endif
    >> +# define NR_IRQ_VECTORS NR_IRQS
    >> +
    >> +#elif !defined(CONFIG_X86_VOYAGER)
    >>
    >> # if defined(CONFIG_X86_IO_APIC) || defined(CONFIG_PARAVIRT) || defined(CONFIG_X86_VISWS)
    >>
    >>
    >
    > what should xen pv 64 get for NR_IRQS?
    >

    Much the same as usual; perhaps a bit lower. 16/CPU would probably be
    ample.

    But given that the kernel also needs to be able to boot native properly,
    just choosing the normal number would be best.

    I long for the day it becomes dynamic...

    J


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