On Mon, Apr 01, 2013 at 02:45:18PM +0900, Takao Indoh wrote: > <Current flow on kdump boot> > enable_IR > intel_enable_irq_remapping > iommu_disable_irq_remapping <== IRES/QIES/TES disabled here > dmar_disable_qi <== do nothing > dmar_enable_qi <== QIES enabled > intel_setup_irq_remapping <== IRES enabled But what we want to do here in the kdumo case is to disable translation too, right? Because the former kernel might have translation and irq-remapping enabled and the kdump kernel might be compiled without support for dma-remapping. So if we don't disable translation here too the kdump kernel is unable to do DMA. I agree that disabling translation should be a bit more explicit instead of the current code. Joerg
