Re: [PATCH v3 2/3] iommu/of: fix device tree configuration for PCI devices

On Thu, Aug 14, 2025 at 07:32:36PM -0700, Shyam Saini wrote:

On Thu, Aug 14, 2025 at 09:39:58PM -0300, Jason Gunthorpe wrote:

quoted

On Thu, Aug 14, 2025 at 04:30:18PM -0700, Shyam Saini wrote:

quoted

or were you referring to [2]?

In that case, the PCI child node data needs to be parsed, which is
currently handled individually by each host controller driver.

Yes, this looks like it may be what I was thinking of, the pci@1,0
specifes the BDF effectively

In that case, we'll need to parse the child DTS nodes properly
within of_iommu_get_resv_regions(). I'll include this in v4.

Kinda surprised this isn't happening already? It would be good to
refer to the original specs and describe how whatetever you propose is
aligned there.

quoted

Presumably this is a fixed issue of the platform. You never did
explain how your system has such werdio behavior, or how something
like iommu=pt can function on it...

Yes, this issue is platform-specific. On this platform, the default MSI IOVA
range overlaps with an address region that is reserved for another purpose,
Other than that we haven't observed any obvious issues for DMA operations

Usually DRAM is at the default MSI IOVA address, so if you run
iommu=pt then presumably your DRAM map has a nice hole in it.. But
maybe the memory map told the OS about that.

Jason