On Mon, 12 Nov 2018 19:06:26 +0300 Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> wrote: > From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> > > Intel VT-d spec added a new DMA_CTRL_PLATFORM_OPT_IN_FLAG flag > in DMAR ACPI table for BIOS to report compliance about platform > initiated DMA restricted to RMRR ranges when transferring control > to the OS. The OS treats this as a hint that the IOMMU should be > enabled to prevent DMA attacks from possible malicious devices. Does this in any way suggest that there are additional recommended uses cases from Intel for RMRRs? My concern here is the incompatibility we have with RMRRs and device assignment as we currently cannot assign devices where the IOVA address space is encumbered by RMRR requirements. Unfortunately RMRRs do not indicate any sort or lifespan, so firmware enabling an RMRR simply to support some boot-time DMA encumbers the device with that RMRR for the life of that boot, unless we have VT-d code that decides it knows better. Thanks, Alex
