linux-kernel - Re: [PATCH] x86_64: Restore the proper NR

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Date:	Sat, 2 Aug 2008 22:58:24 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Jeremy Fitzhardinge" <jeremy@...p.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>, "Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Dhaval Giani" <dhaval@...ux.vnet.ibm.com>,
	"Mike Travis" <travis@....com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86_64: Restore the proper NR_IRQS define so larger systems work.

On Sat, Aug 2, 2008 at 10:26 PM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
>
> As pointed out and tracked by Yinghai Lu <yhlu.kernel@...il.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@...utronix.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@...ux.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@...ssion.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?

YH
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