Re: [3/3] Use the DMA32 zone for dma_alloc_coherent()/pci_alloc_consistent on x86-64

[Linus Torvalds <torvalds@osdl.org>]

On Sun, 11 Sep 2005, Andi Kleen wrote:
>
> Use the DMA32 zone for dma_alloc_coherent()/pci_alloc_consistent on x86-64
> 
> Signed-off-by: Andi Kleen <ak@suse.de>
> 
> Index: linux/arch/x86_64/kernel/pci-gart.c
> ===================================================================
> --- linux.orig/arch/x86_64/kernel/pci-gart.c
> +++ linux/arch/x86_64/kernel/pci-gart.c
> @@ -219,6 +219,8 @@ dma_alloc_coherent(struct device *dev, s
>  	/* Kludge to make it bug-to-bug compatible with i386. i386
>  	   uses the normal dma_mask for alloc_coherent. */
>  	dma_mask &= *dev->dma_mask;
> +	if (dma_mask <= 0xffffffff)
> +		gfp |= GFP_DMA32;

How can this be right?

Let's say that dma_mask is 0xfffff (ie 20-bit legacy DMA). It will trigger 
the test, and set the GFP_DMA32 bit. Which can't be right.

I'm going to drop the DMA32 parts of the patches, they seem to be pretty 
raw.

		Linus
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