Re: [PATCH] gurantee DMA area for alloc_bootmem_low()

["Martin J. Bligh" <mbligh@mbligh.org>]

> This is a patch to guarantee that alloc_bootmem_low() allocate DMA area.
> 
> Current alloc_bootmem_low() is just specify "goal=0". And it is 
> used for __alloc_bootmem_core() to decide which address is better.
> However, there is no guarantee that __alloc_bootmem_core()
> allocate DMA area when goal=0 is specified.
> Even if there is no DMA'ble area in searching node, it allocates
> higher address than MAX_DMA_ADDRESS.
> 
> __alloc_bootmem_core() is called by order of for_each_pgdat()
> in __alloc_bootmem(). So, if first node (node_id = 0) has
> DMA'ble area, no trouble will occur. However, our new Itanium2 server
> can change which node has lower address. And panic really occurred on it.
> The message was "bounce buffer is not DMA'ble" in swiothl_map_single().
> 
> To avoid this panic, following patch skips no DMA'ble node when 
> lower address is required.
> I tested this patch on my Tiger 4 and our new server.

Seems reasonable ... but do you not want to check that the returned
ptr is actually less than MAX_DMA_ADDRESS as well? 

> Please apply.
> 
> Thanks.
> 
> Signed-off by Yasunori Goto <y-goto@jp.fujitsu.com>
> 
> Index: allocbootmem/mm/bootmem.c
> ===================================================================
> --- allocbootmem.orig/mm/bootmem.c	2005-06-30 11:57:13.000000000 +0900
> +++ allocbootmem/mm/bootmem.c	2005-07-08 20:46:56.209040741 +0900
> @@ -387,10 +387,16 @@
>  	pg_data_t *pgdat = pgdat_list;
>  	void *ptr;
>  
> -	for_each_pgdat(pgdat)
> +	for_each_pgdat(pgdat){
> +
> +		if (goal < __pa(MAX_DMA_ADDRESS) &&
> +		    pgdat->bdata->node_boot_start >= __pa(MAX_DMA_ADDRESS))
> +			continue; /* Skip No DMA node */
> +
>  		if ((ptr = __alloc_bootmem_core(pgdat->bdata, size,
>  						align, goal)))
>  			return(ptr);
> +	}
>  
>  	/*
>  	 * Whoops, we cannot satisfy the allocation request.
> 
> -- 
> Yasunori Goto 
> 
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