Re: [PATCH v7 10/19] xen: add hook for AP bootstrap memory reservation

On Thu, Dec 19, 2013 at 07:54:47PM +0100, Roger Pau Monne wrote:
> This hook will only be implemented for bare metal, Xen doesn't require
> any bootstrap code since APs are started in long mode with paging
> enabled.
> ---
>  sys/amd64/amd64/machdep.c   |    6 +++++-
>  sys/amd64/include/sysarch.h |    3 +++
>  2 files changed, 8 insertions(+), 1 deletions(-)
> 
> diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
> index 6bbfe5a..a811a9b 100644
> --- a/sys/amd64/amd64/machdep.c
> +++ b/sys/amd64/amd64/machdep.c
> _at__at_ -186,6 +186,9 _at__at_ struct init_ops init_ops = {
>  	.early_delay_init =	i8254_init,
>  	.early_delay =		i8254_delay,
>  	.parse_memmap =		native_parse_memmap,
> +#ifdef SMP
> +	.mp_bootaddress =	mp_bootaddress,
> +#endif
>  };
>  
>  /*
> _at__at_ -1507,7 +1510,8 _at__at_ getmemsize(caddr_t kmdp, u_int64_t first)
>  
>  #ifdef SMP
>  	/* make hole for AP bootstrap code */
> -	physmap[1] = mp_bootaddress(physmap[1] / 1024);
> +	if (init_ops.mp_bootaddress)
> +		physmap[1] = init_ops.mp_bootaddress(physmap[1] / 1024);
>  #endif
>  
>  	/*
> diff --git a/sys/amd64/include/sysarch.h b/sys/amd64/include/sysarch.h
> index 084223e..77f4b29 100644
> --- a/sys/amd64/include/sysarch.h
> +++ b/sys/amd64/include/sysarch.h
> _at__at_ -16,6 +16,9 _at__at_ struct init_ops {
>  	void	(*early_delay_init)(void);
>  	void	(*early_delay)(int);
>  	void	(*parse_memmap)(caddr_t, vm_paddr_t *, int *);
> +#ifdef SMP
> +	u_int	(*mp_bootaddress)(u_int);
> +#endif
>  };
>  
>  extern struct init_ops init_ops;

I suggest to make the init_ops contain the mp_bootaddress unconditionally,
instead of making it depended on SMP.  The #ifdef makes the kernel binary
interface fragile and depended on the config, which would cause problems
in future if any module needs any interation with init_ops.