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Subject: Re: [PATCH] powerpc: remove WARN_ON() from dma-noncoherent.c
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Hollis Blanchard <hollisb@us.ibm.com>
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Date: Tue, 11 Nov 2008 13:09:04 +1100
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On Mon, 2008-11-10 at 18:33 -0600, Hollis Blanchard wrote:
> I can't tell why this WARN_ON exists, and there's no comment explaining it.
> Whether the pmd is present or not, pte_alloc_kernel() seems to handle both
> cases.
> 
> Booting a 440 kernel with 64K PAGE_SIZE triggers the warning, but boot
> successfully completes and I see no problems beyond that.
> 
> Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>

I can't see any reason neither off hand, so

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Ben.
> ---
> 
> Large page support is critical for improving KVM performance, so I'd like this
> apparently unnecessary warning to be removed to make way for Ilya's patch.
> 
> Vitaly, this code was added by you in Feb 2007. Any thoughts?
> 
> diff --git a/arch/powerpc/lib/dma-noncoherent.c b/arch/powerpc/lib/dma-noncoherent.c
> --- a/arch/powerpc/lib/dma-noncoherent.c
> +++ b/arch/powerpc/lib/dma-noncoherent.c
> @@ -320,7 +320,6 @@ static int __init dma_alloc_init(void)
>  			ret = -ENOMEM;
>  			break;
>  		}
> -		WARN_ON(!pmd_none(*pmd));
>  
>  		pte = pte_alloc_kernel(pmd, CONSISTENT_BASE);
>  		if (!pte) {
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