On Fri, May 14, 2021 at 06:54:16AM +0000, Tian, Kevin wrote: > > From: Tian, Kevin > > Sent: Friday, May 14, 2021 2:28 PM > > > > > From: Jason Gunthorpe <jgg@xxxxxxxx> > > > Sent: Thursday, May 13, 2021 8:01 PM > > > > > > On Thu, May 13, 2021 at 03:28:52AM +0000, Tian, Kevin wrote: > > > > > > > Are you specially concerned about this iommu_device hack which > > > > directly connects mdev_device to iommu layer or the entire removed > > > > logic including the aux domain concept? For the former we are now > > > > following up the referred thread to find a clean way. But for the latter > > > > we feel it's still necessary regardless of how iommu interface is > > redesigned > > > > to support device connection from the upper level driver. The reason is > > > > that with mdev or subdevice one physical device could be attached to > > > > multiple domains now. there could be a primary domain with DOMAIN_ > > > > DMA type for DMA_API use by parent driver itself, and multiple auxiliary > > > > domains with DOMAIN_UNMANAGED types for subdevices assigned to > > > > different VMs. > > > > > > Why do we need more domains than just the physical domain for the > > > parent? How does auxdomain appear in /dev/ioasid? > > > > > > > Say the parent device has three WQs. WQ1 is used by parent driver itself, > > while WQ2/WQ3 are assigned to VM1/VM2 respectively. > > > > WQ1 is attached to domain1 for an IOVA space to support DMA API > > operations in parent driver. More specifically WQ1 uses a PASID that is represented by an IOASID to userspace. > > WQ2 is attached to domain2 for the GPA space of VM1. Domain2 is > > created when WQ2 is assigned to VM1 as a mdev. > > > > WQ3 is attached to domain3 for the GPA space of VM2. Domain3 is > > created when WQ3 is assigned to VM2 as a mdev. > > > > In this case domain1 is the primary while the other two are auxiliary > > to the parent. > > > > auxdomain represents as a normal domain in /dev/ioasid, with only > > care required when doing attachment. > > > > e.g. VM1 is assigned with both a pdev and mdev. Qemu creates > > gpa_ioasid which is associated with a single domain for VM1's > > GPA space and this domain is shared by both pdev and mdev. > > Here pdev/mdev are just conceptual description. Following your > earlier suggestion /dev/ioasid will not refer to explicit mdev_device. > Instead, each vfio device attached to an ioasid is represented by either > "struct device" for pdev or "struct device + pasid" for mdev. The > presence of pasid decides which iommu_attach api should be used. But you still haven't explained what an aux domain is to /dev/ioasid. Why do I need more public kernel objects to represent a PASID IOASID? Are you creating a domain for every IOASID? Why? Jason
