* Vivek Goyal (vgoyal at redhat.com) wrote: > On Wed, Mar 31, 2010 at 02:25:35PM -0700, Chris Wright wrote: > > * Neil Horman (nhorman at tuxdriver.com) wrote: > > > Flush iommu during shutdown > > > > > > When using an iommu, its possible, if a kdump kernel boot follows a primary > > > kernel crash, that dma operations might still be in flight from the previous > > > kernel during the kdump kernel boot. This can lead to memory corruption, > > > crashes, and other erroneous behavior, specifically I've seen it manifest during > > > a kdump boot as endless iommu error log entries of the form: > > > AMD-Vi: Event logged [IO_PAGE_FAULT device=00:14.1 domain=0x000d > > > address=0x000000000245a0c0 flags=0x0070] > > > > We've already fixed this problem once before, so some code shift must > > have brought it back. Personally, I prefer to do this on the bringup > > path than the teardown path. Besides keeping the teardown path as > > simple as possible (goal is to get to kdump kernel asap), there's also > > reason to competely flush on startup in genernal in case BIOS has done > > anything unsavory. > > Can we flush domains (all the I/O TLBs assciated with each domain), during > initialization? I think all the domain data built by previous kernel will > be lost and new kernel will have no idea about. We first invalidate the device table entry, so new translation requests will see the new domainid for a given BDF. Then we invalidate the whole set of page tables associated w/ the new domainid. Now all dma transactions will need page table walk (page tables will be empty excpet for any 1:1 mappings). Any old domainid's from previous kernel that aren't found in new device table entries are effectively moot. Just so happens that in kexec/kdump case, they'll be the same domainid's, but that doesn't matter. thanks, -chris
