Re: [PATCH v6 01/16] iommu/dma: Prepare MSI physical address lists

[Jason Gunthorpe]

On Sat, Oct 03, 2026 at 02:03:35PM +0200, Andrew Jones wrote:
> 
> Hi Robin,
> 
> On Fri, Oct 02, 2026 at 05:21:18PM +0100, Robin Murphy wrote:
> > You already end up adding what is effectively a RISC-V-specific
> > entrypoint, so you may as well just carry that all the way through to
> > its own effectively RISC-V-specific implementation
> 
> The list API came out of the v4[1] discussion with Jason. Preparing the
> targets as one contiguous IOVA range lets the MSI descriptor cache the
> base and IMSIC compose the address as base + CPU offset. That got
> rid of the separate domain-local lookup table and its lifetime handling,
> which I think was a worthwhile improvement.

Yeah, I prefer this idea to what you had earlier, however it is
accomodated.

> > it should merely be a case of whether a) this is the first call for
> > the given cookie so everything needs mapping, or b) it's not the
> > first call, so everything must already be mapped and we can just
> > return the IOVA.
> 
> For DMA-IOMMU, yes, remembering the base would let us drop the range
> matching. We'd still need the contiguous IOVA allocation, mapping loop,
> rollback on failure, and locking across the whole operation.

I fell like dma-iommu should have a way to map a page list to iova and
maybe that is all the shared code with arm there is.

Jason