From: Jason Gunthorpe <jgg@xxxxxxxxxx>
Sent: Tuesday, May 24, 2022 9:39 PM
On Tue, May 24, 2022 at 09:39:52AM +0000, Tian, Kevin wrote:
IOMMUFrom: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Sent: Thursday, May 19, 2022 3:21 PM
The iommu_sva_domain represents a hardware pagetable that the
hardware could use for SVA translation. This adds some infrastructure
to support SVA domain in the iommu common layer. It includes:
- Add a new struct iommu_sva_domain and new IOMMU_DOMAIN_SVA
domain
type.
- Add a new domain ops pointer in iommu_ops. The IOMMU drivers that
support SVA should provide the callbacks.
- Add helpers to allocate and free an SVA domain.
- Add helpers to set an SVA domain to a device and the reverse
operation.
Some buses, like PCI, route packets without considering the PASID value.
Thus a DMA target address with PASID might be treated as P2P if the
address falls into the MMIO BAR of other devices in the group. To make
things simple, the attach/detach interfaces only apply to devices
belonging to the singleton groups, and the singleton is immutable in
fabric i.e. not affected by hotplug.
The iommu_set/block_device_pasid() can be used for other purposes,
such as kernel DMA with pasid, mediation device, etc. Hence, it is put
in the iommu.c.
usually we have 'set/clear' pair or 'allow/block'. Having 'set' paired
with 'block' doesn't read very clearly.
I thought we agreed we'd use the blocking domain for this? Why did it
go back to an op?
Probably it's based on following discussion:
https://lore.kernel.org/all/c8492b29-bc27-ae12-d5c4-9fbbc797e310@xxxxxxxxxxxxxxx/
--
FWIW from my point of view I'm happy with having a .detach_dev_pasid op
meaning implicitly-blocked access for now.
If this is the path then lets not call it attach/detach
please. 'set_dev_pasid' and 'set_dev_blocking_pasid' are clearer
names.
--
Looks Baolu chooses this path and plans to use the blocking domain
later.