[PATCH] Document iommu=panic

Signed-off-by: NAndi Kleen <ak@suse.de>

Documentation/x86_64/boot-options.txt

@@ -203,6 +203,7 @@ IOMMU
 	    When off all DMA over >4GB is forced through an IOMMU or bounce
 	    buffering.
    nodac    Forbid DMA >4GB
+   panic    Always panic when IOMMU overflows
 
   swiotlb=pages[,force]
 

arch/x86_64/kernel/pci-dma.c

@@ -245,6 +245,7 @@ EXPORT_SYMBOL(dma_set_mask);
    noaperture Don't touch the aperture for AGP.
    allowdac Allow DMA >4GB
    nodac    Forbid DMA >4GB
+   panic    Force panic when IOMMU overflows
 */
 __init int iommu_setup(char *p)
 {