On Wed, Jun 02, 2021 at 04:52:02PM +0800, Jason Wang wrote: > > 在 2021/6/2 上午4:28, Jason Gunthorpe 写道: > > > I summarized five opens here, about: > > > > > > 1) Finalizing the name to replace /dev/ioasid; > > > 2) Whether one device is allowed to bind to multiple IOASID fd's; > > > 3) Carry device information in invalidation/fault reporting uAPI; > > > 4) What should/could be specified when allocating an IOASID; > > > 5) The protocol between vfio group and kvm; > > > > > > For 1), two alternative names are mentioned: /dev/iommu and > > > /dev/ioas. I don't have a strong preference and would like to hear > > > votes from all stakeholders. /dev/iommu is slightly better imho for > > > two reasons. First, per AMD's presentation in last KVM forum they > > > implement vIOMMU in hardware thus need to support user-managed > > > domains. An iommu uAPI notation might make more sense moving > > > forward. Second, it makes later uAPI naming easier as 'IOASID' can > > > be always put as an object, e.g. IOMMU_ALLOC_IOASID instead of > > > IOASID_ALLOC_IOASID.:) > > I think two years ago I suggested /dev/iommu and it didn't go very far > > at the time. > > > It looks to me using "/dev/iommu" excludes the possibility of implementing > IOASID in a device specific way (e.g through the co-operation with device > MMU + platform IOMMU)? This is intended to be the 'drivers/iommu' subsystem though. I don't want to see pluggabilit here beyoned what drivers/iommu is providing. If someone wants to do a something complicated through this interface then they need to make a drivers/iommu implementation. Or they need to use the mdev-esque "SW TABLE" mode when their driver attaches to the interface. If this is good enough or not for a specific device is an entirely other question though > What's more, ATS spec doesn't forbid the device #PF to be reported via a > device specific way. And if this is done then a kernel function indicating page fault should be triggered on the ioasid handle that the device has. It is still drivers/iommu functionality Jason
