Re: [PATCH] x86: fix probe_nr_irqs for xen

[Jeremy Fitzhardinge <jeremy@goop.org>]

Yinghai Lu wrote:
> otherwise Xen is _completely_ unusable with 5 or more VCPUs.
> ( when !CONFIG_HAVE_SPARSE_IRQ)
>
> based on Alex's patch
>
> also add +1 offset after redir_entries
>
> Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
> Cc: Alex Nixon <alex.nixon@citrix.com>
>   

Looks good to me.  We can fix this in a better way later.

Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

> Index: linux-2.6/arch/x86/kernel/io_apic.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/io_apic.c
> +++ linux-2.6/arch/x86/kernel/io_apic.c
> @@ -3625,16 +3625,21 @@ int __init probe_nr_irqs(void)
>  {
>  	int idx;
>  	int nr = 0;
> +#ifndef CONFIG_XEN
> +	int nr_min = 32;
> +#else
> +	int nr_min = NR_IRQS;
> +#endif
>  
>  	for (idx = 0; idx < nr_ioapics; idx++)
> -		nr += io_apic_get_redir_entries(idx);
> +		nr += io_apic_get_redir_entries(idx) + 1;
>  
>  	/* double it for hotplug and msi and nmi */
>  	nr <<= 1;
>  
>  	/* something wrong ? */
> -	if (nr < 32)
> -		nr = 32;
> +	if (nr < nr_min)
> +		nr = nr_min;
>  
>  	return nr;
>  }
> --
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