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

Hi Jason,

On Mon, Aug 18, 2025 at 12:53:10PM -0300, Jason Gunthorpe wrote:

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

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

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

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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.

Just to confirm, does the v3 version of this series look good to you?
If so, I’ll go ahead and respin the series with the iommu_set_sw_msi()
change and address the other review comments from Jacob.

Otherwise having pci devices nodes in the fdt or dts needs additional
handling, let me know your preference :)

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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.

 
our DRAM for this platform starts at higher offset, way beyond MSI_IOVA.


Thanks,
Shyam