> From: Malcolm Crossley > Sent: Tuesday, December 09, 2014 6:52 PM > > On 09/12/14 10:37, Yu, Zhang wrote: > > > > > > On 12/9/2014 6:19 PM, Paul Durrant wrote: > >> I think use of an raw mfn value currently works only because dom0 is > >> using a 1:1 IOMMU mapping scheme. Is my understanding correct, or do > >> you really need raw mfn values? > > Thanks for your quick response, Paul. > > Well, not exactly for this case. :) > > In XenGT, our need to translate gfn to mfn is for GPU's page table, > > which contains the translation between graphic address and the memory > > address. This page table is maintained by GPU drivers, and our service > > domain need to have a method to translate the guest physical addresses > > written by the vGPU into host physical ones. > > We do not use IOMMU in XenGT and therefore this translation may not > > necessarily be a 1:1 mapping. > > XenGT must use the IOMMU mappings that Xen has setup for the domain > which owns the GPU. Currently Dom0 own's the GPU and so it's IOMMU > mappings match the MFN's addresses. I suspect XenGT will not work if Xen > is booted with iommu=dom0-strict. >
This is a good point. So yes in this case IOMMU is still active which contains a 1:1 IOMMU mapping table, but it's a separate thing from the interface discussed here, which is about setup a shadow GPU page table for other VM's graphics memory accesses. Thanks Kevin _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
