Date: Tue, 18 Oct 2005 13:28:20 +0900
From: Yasunori Goto <y-goto@jp.fujitsu.com>
To: Ravikiran G Thirumalai <kiran@scalex86.org>
Subject: Re: [discuss] Re: x86_64: 2.6.14-rc4 swiotlb broken
Cc: Linus Torvalds <torvalds@osdl.org>, Muli Ben-Yehuda <mulix@mulix.org>,
       Andi Kleen <ak@suse.de>, discuss@x86-64.org,
       Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org,
       tglx@linutronix.de, shai@scalex86.org, clameter@engr.sgi.com,
       muli@il.ibm.com, jdmason@us.ibm.com
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> > So, just "use NODE(0)" is not enough hack for our machine.
> > If "use NODE(0)" is selected, kernel must sort pgdat link and
> > node id by memory address. I think that hot add code will be a 
> > bit messy instead.
> 
> Yasunori-san,
> Does this patch work on your boxes instead? (For 2.6.14)
> http://marc.theaimsgroup.com/?l=linux-kernel&m=112959469914681&w=2

Not yet. But could you change this line at least?

+	
+	for_each_node(node) {
+		io_tlb_start = alloc_bootmem_node(NODE_DATA(node), iotlbsz);

for_each_node() loop walks around node_possible_map which includes
"offlined" node. 
Please use for_each_online_node() instead. Then, I'll check it. :-)


And I understand why my patch doesn't work on your box by
your patch. (Thanks!)
x86-64's DMA zone is smaller area than 16MB.
But swiotlb requires the area which is smaller than 4GB.
There is no interface to describe its difference.

I think your patch looks reasonable for 2.6.14 to be produced ASAP.
This is less impact than mine. 

However, kernel should have new interface like alloc_bootmmem_low32().
This problem will occur not only by swiotlb.

I'll rewrite my patch to make it. If it is applied at 2.6.15,
I'll be glad.

Thanks.

-- 
Yasunori Goto 

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