[RFC] Start SMP subsystem earlier

[Hans Petter Selasky]

Hi,

There is a limitiation on the number of interrupt vectors available when 
only a single processor is running. To have more interrupts available we 
need to start SMP earlier when building a monotolith kernel and not 
loading drivers as modules. The driver in question is a network driver 
and because it cannot be started after SI_SUB_ROOT_CONF due to PXE 
support I see no other option than to move SI_SUB_SMP earlier.

Suggested patch:

> Index: sys/kernel.h
> ===================================================================
> --- sys/kernel.h	(revision 276691)
> +++ sys/kernel.h	(working copy)
> @@ -152,6 +152,7 @@
>  	SI_SUB_KPROF		= 0x9000000,	/* kernel profiling*/
>  	SI_SUB_KICK_SCHEDULER	= 0xa000000,	/* start the timeout events*/
>  	SI_SUB_INT_CONFIG_HOOKS	= 0xa800000,	/* Interrupts enabled config */
> +	SI_SUB_SMP		= 0xa850000,	/* start the APs*/
>  	SI_SUB_ROOT_CONF	= 0xb000000,	/* Find root devices */
>  	SI_SUB_DUMP_CONF	= 0xb200000,	/* Find dump devices */
>  	SI_SUB_RAID		= 0xb380000,	/* Configure GEOM classes */
> @@ -165,7 +166,6 @@
>  	SI_SUB_KTHREAD_BUF	= 0xea00000,	/* buffer daemon*/
>  	SI_SUB_KTHREAD_UPDATE	= 0xec00000,	/* update daemon*/
>  	SI_SUB_KTHREAD_IDLE	= 0xee00000,	/* idle procs*/
> -	SI_SUB_SMP		= 0xf000000,	/* start the APs*/
>  	SI_SUB_RACCTD		= 0xf100000,	/* start racctd*/
>  	SI_SUB_LAST		= 0xfffffff	/* final initialization */
>  };

This fixes a problem for Mellanox drivers in the OFED layer. Possibly we 
need to move the SMP even earlier to not miss the generic FreeBSD PCI 
device enumeration or maybe this is not possible. Does anyone know how 
early we can start SMP?

--HPS