Re: [Xen-devel] [PATCH] x86: fix off-by-one in nr_irqs_gsi calculation

[Keir Fraser <keir@xxxxxxx>]

On 26/07/2012 16:06, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:

> highest_gsi() returns the last valid GSI, not a count.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Why not "nr_irqs_gsi = max(nr_irqs_gsi, highest_gsi()+1)"?

> --- a/xen/arch/x86/io_apic.c
> +++ b/xen/arch/x86/io_apic.c
> @@ -2531,7 +2531,9 @@ void __init init_ioapic_mappings(void)
>          }
>      }
>  
> -    nr_irqs_gsi = max(nr_irqs_gsi, highest_gsi());
> +    i = highest_gsi();
> +    if ( i >= nr_irqs_gsi )
> +        nr_irqs_gsi = i + 1;
>  
>      if ( max_gsi_irqs == 0 )
>          max_gsi_irqs = nr_irqs ? nr_irqs / 8 : PAGE_SIZE;
> 
> 
> 
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