Messages in this thread | | | Subject | Re: [PATCH 0/7] iommu cleanup and refactoring | From | Lu Baolu <> | Date | Wed, 26 Jan 2022 09:51:36 +0800 |
| |
On 1/25/22 11:16 PM, Jason Gunthorpe wrote: > On Tue, Jan 25, 2022 at 02:48:02PM +0000, Robin Murphy wrote: > >> Agreed, certainly an IOMMU_DOMAIN_SVA type that can both encapsulate the mm >> and effectively replace iommu_sva seems like a logical and fairly small next >> step. We already have the paradigm of different domain types supporting >> different ops, so initially an SVA domain would simply allow bind/unbind >> rather than attach/detach/map/unmap. > > I hope we can quickly get to a PASID enabled generic attach/detach > scheme - we really need this to do the uAPI part of this interface.
Agreed. Jacob is working on kernel DMA with PASID. He needs such interfaces as well. I have worked out an implementation for vt-d driver. It could be post for review inside Jacob's series for kernel DMA with PASID.
> >> they are fundamentally different things in their own right, and the ideal >> API should give us the orthogonality to also bind a device to an SVA domain >> without PASID (e.g. for KVM stage 2, or userspace assignment of simpler >> fault/stall-tolerant devices), or attach PASIDs to regular iommu_domains. > > Yes, these are orthogonal things. A iommu driver that supports PASID > ideally should support PASID enabled attach/detatch for every > iommu_domain type it supports. > > SVA should not be entangled with PASID beyond that SVA is often used > with PASID - a SVA iommu_domain should be fully usable with a RID too.
The prototype of PASID enabled attach/detach ops could look like:
int (*attach_dev_pasid)(struct iommu_domain *domain, struct device *dev, ioasid_t id); void (*detach_dev_pasid)(struct iommu_domain *domain, struct device *dev, ioasid_t id);
But the iommu driver should implement different callbacks for
1) attaching an IOMMU DMA domain to a PASID on device; - kernel DMA with PASID - mdev-like device passthrough - etc. 2) attaching a CPU-shared domain to a PASID on device; - SVA - guest PASID - etc.
> > I'm hoping to see the core iommu code provide some simplified "SVA" > API that under the covers creates a SVA domain and then does a normal > PASID attach using the global PASID in the mm_struct - the > driver should not care what, or even if, PASID is used for a SVA > domain. > > Jason >
Best regards, baolu
| |