Re: [PATCH v6 00/16] dma-mapping: migrate to physical address-based API

Keith Busch
2025-09-23T18:30:59Z

On Tue, Sep 23, 2025 at 02:09:36PM -0300, Jason Gunthorpe wrote:
> On Sat, Sep 20, 2025 at 06:47:27PM -0600, Keith Busch wrote:
> >
> > One other thing to note, this was runing on arm64 platform using smmu
> > configured with 64k pages. If your iommu granule is 4k instead, we
> > wouldn't use the blk_dma_map_direct path.
>
> I spent some time looking to see if I could guess what this is and
> came up empty. It seems most likely we are leaking a dma mapping
> tracking somehow? The DMA API side is pretty simple here though..

Yeah, nothing stood out to me here either.

> Not sure the 64k/4k itself is a cause, but triggering the non-iova
> flow is probably the issue.
>
> Can you check the output of this debugfs:

I don't have a system in this state at the moment, so we checked
previous logs on machines running older kernels. It's extermely
uncommon, but this error was happening prior to this series, so I don't
think this introduced any new problem here. I'll keeping looking, but I
don't think we'll make much progress if I can't find a more reliable
reproducer.

Thanks!