x86_64: Fail dma_alloc_coherent on dma less devices

This should fix an oops with PCMCIA PATA devices

http://bugzilla.kernel.org/show_bug.cgi?id=8424

This is not a full fix for the problem, but probably
still the right thing to do.

[ I'm almost certain it's *not* the right thing to do, but it avoids an
oops, and I want comments from others on what the right thing would
actually be.. I suspect we should just remove the use of dma_mask
entirely in this function, and just use coherent_dma_mask. - Linus ]

Signed-off-by: Andi Kleen <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/x86_64/kernel/pci-dma.c

···
 	if (dma_mask == 0)
 		dma_mask = DMA_32BIT_MASK;
 
+	/* Device not DMA able */
+	if (dev->dma_mask == NULL)
+		return NULL;
+
 	/* Don't invoke OOM killer */
 	gfp |= __GFP_NORETRY;