On Tue, Jun 01, 2021 at 02:03:33PM +1000, David Gibson wrote: > On Thu, May 27, 2021 at 03:48:47PM -0300, Jason Gunthorpe wrote: > > On Thu, May 27, 2021 at 02:58:30PM +1000, David Gibson wrote: > > > On Tue, May 25, 2021 at 04:52:57PM -0300, Jason Gunthorpe wrote: > > > > On Wed, May 26, 2021 at 12:56:30AM +0530, Kirti Wankhede wrote: > > > > > > > > > 2. iommu backed mdev devices for SRIOV where mdev device is created per > > > > > VF (mdev device == VF device) then that mdev device has same iommu > > > > > protection scope as VF associated to it. > > > > > > > > This doesn't require, and certainly shouldn't create, a fake group. > > > > > > It's only fake if you start with a narrow view of what a group is. > > > > A group is connected to drivers/iommu. A group object without *any* > > relation to drivers/iommu is just a complete fiction, IMHO. > > That might be where we differ. As I've said, my group I'm primarily > meaning the fundamental hardware unit of isolation. *Usually* that's > determined by the capabilities of an IOMMU, but in some cases it might > not be. In either case, the boundaries still matter. As in my other email we absolutely need a group concept, it is just a question of how the user API is designed around it. > > The group mdev implicitly creates is just a fake proxy that comes > > along with mdev API. It doesn't do anything and it doesn't mean > > anything. > > But.. the case of multiple mdevs managed by a single PCI device with > an internal IOMMU also exists, and then the mdev groups are *not* > proxies but true groups independent of the parent device. Which means > that the group structure of mdevs can vary, which is an argument *for* > keeping it, not against. If VFIO becomes more "vfio_device" centric then the vfio_device itself has some properties. One of those can be "is it inside a drivers/iommu group, or not?". If the vfio_device is not using a drivers/iommu IOMMU interface then it can just have no group at all - no reason to lie. This would mean that the device has perfect isolation. What I don't like is forcing certain things depending on how the vfio_device was created - for instance forcing a IOMMU group as part and forcing an ugly "SW IOMMU" mode in the container only as part of mdev_device. These should all be properties of the vfio_device itself. Again this is all about the group fd - and how to fit in with the /dev/ioasid proposal from Kevin: https://lore.kernel.org/kvm/MWHPR11MB1886422D4839B372C6AB245F8C239@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ Focusing on vfio_device and skipping the group fd smooths out some rough edges. Code wise we are not quite there, but I have mapped out eliminating the group from the vfio_device centric API and a few other places it has crept in. The group can exist in the background to enforce security without being a cornerstone of the API design. Jason
