On Fri, 30 Jul 2010, Vivek Goyal wrote: > On Fri, Jul 30, 2010 at 11:21:42AM -0700, Eric W. Biederman wrote: >> David Woodhouse <dwmw2 at infradead.org> writes: >> >>> On Thu, 2010-07-29 at 21:41 -0700, Eric W. Biederman wrote: >>>> There isn't a bus master shut off at the core level. >>> >>> Effectively, there is if you have an IOMMU. >> >> Depends on the IOMMU. There are several dinky IOMMUs that when you >> shut them off DMA simply goes around them, and is not stopped. > > I think last time we were discussing this for AMD IOMMU where if you > disable IOMMU, it just kind of become pass through with 1:1 mapping of > addresses. Yeah, don't do that. The IOMMU should be *on*, but without any active mappings set up. Which is exactly how Linux will set it up at boot. -- dwmw2
