On Thu, May 13, 2021 at 04:07:07PM +1000, David Gibson wrote: > On Wed, May 05, 2021 at 01:39:02PM -0300, Jason Gunthorpe wrote: > > On Wed, May 05, 2021 at 02:28:53PM +1000, Alexey Kardashevskiy wrote: > > > > > This is a good feature in general when let's say there is a linux supported > > > device which has a proprietary device firmware update tool which only exists > > > as an x86 binary and your hardware is not x86 - running qemu + vfio in full > > > emulation would provide a way to run the tool to update a physical device. > > > > That specific use case doesn't really need a vIOMMU though, does it? > > Possibly not, but the mechanics needed to do vIOMMU on different host > IOMMU aren't really different from what you need for a no-vIOMMU > guest. For very simple vIOMMUs this might be true, but this new features of nesting PASID, migration, etc, etc all make the vIOMMU complicated and emuluating it completely alot harder. Stuffing a vfio-pci into a guest and creating a physical map using a single IOASID is comparably trivial. Jason
