On Wed, Apr 22, 2020 at 12:53:25AM +0000, Tian, Kevin wrote: > > From: Jason Gunthorpe > > Sent: Wednesday, April 22, 2020 7:55 AM > > > > On Tue, Apr 21, 2020 at 04:33:46PM -0700, Dave Jiang wrote: > > > The actual code is independent of the stage 2 driver code submission that > > adds > > > support for SVM, ENQCMD(S), PASID, and shared workqueues. This code > > series will > > > support dedicated workqueue on a guest with no vIOMMU. > > > > > > A new device type "mdev" is introduced for the idxd driver. This allows the > > wq > > > to be dedicated to the usage of a VFIO mediated device (mdev). Once the > > work > > > queue (wq) is enabled, an uuid generated by the user can be added to the > > wq > > > through the uuid sysfs attribute for the wq. After the association, a mdev > > can > > > be created using this UUID. The mdev driver code will associate the uuid > > and > > > setup the mdev on the driver side. When the create operation is successful, > > the > > > uuid can be passed to qemu. When the guest boots up, it should discover a > > DSA > > > device when doing PCI discovery. > > > > I'm feeling really skeptical that adding all this PCI config space and > > MMIO BAR emulation to the kernel just to cram this into a VFIO > > interface is a good idea, that kind of stuff is much safer in > > userspace. > > > > Particularly since vfio is not really needed once a driver is using > > the PASID stuff. We already have general code for drivers to use to > > attach a PASID to a mm_struct - and using vfio while disabling all the > > DMA/iommu config really seems like an abuse. > > Well, this series is for virtualizing idxd device to VMs, instead of > supporting SVA for bare metal processes. idxd implements a > hardware-assisted mediated device technique called Intel Scalable > I/O Virtualization, I'm familiar with the intel naming scheme. > which allows each Assignable Device Interface (ADI, e.g. a work > queue) tagged with an unique PASID to ensure fine-grained DMA > isolation when those ADIs are assigned to different VMs. For this > purpose idxd utilizes the VFIO mdev framework and IOMMU aux-domain > extension. Bare metal SVA will be enabled for idxd later by using > the general SVA code that you mentioned. Both paths will co-exist > in the end so there is no such case of disabling DMA/iommu config. Again, if you will have a normal SVA interface, there is no need for a VFIO version, just use normal SVA for both. PCI emulation should try to be in userspace, not the kernel, for security. Jason
