On Fri, Jul 30, 2010 at 07:50:19PM +0100, David Woodhouse wrote: > 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. > So what happens if we tear down the mapping while DMA is on. Vivek
