> From: Peter Xu [mailto:pet...@redhat.com] > Sent: Friday, January 20, 2017 6:04 PM > > On Fri, Jan 20, 2017 at 09:52:01AM +0000, Tian, Kevin wrote: > > [...] > > > btw what about guest setups a valid mapping at 0xFEEx_xxxx in > > its remapping structure, which is then programmed to virtual > > device as DMA destination? Then when emulating that virtual DMA, > > vtd_do_iommu_translate should simply return (maybe throw out > > a warning for diagnostic purpose) instead of assert here. > > > > VT-d spec defines as below: > > > > Software must ensure the second-level paging-structure entries > > are programmed not to remap input addresses to the interrupt > > address range. Hardware behavior is undefined for memory > > requests remapped to the interrupt address range. > > Thanks for this reference. That's something I was curious about. > > > > > I don't think "hardware behavior is undefined" is equal to "assert > > thus kill VM"... > > I don't think it will kill the VM. After we have the MSI region, it > should just use that IR region for everything (read/write/translate). > So iiuc when anyone setups IOVA mapping within range 0xfeexxxxx, then > a DMA will trigger an interrupt (rather than memory moves), but in > most cases the interrupt will be illegal since either the data is > invalid (e.g., non-zero reserved bits, or SID verification failure), > further it should trigger a vIOMMU fault (though IR fault reporting is > still incomplete, that's my next thing to do after this series). >
Yes, you're right here. Sorry for bothering with my wrong understanding. :-) Thanks Kevin
