Why reports a "Transaction type disallowed" fault when the IOVA is determined to be that of a virtual interrupt file and the corresponding MSI PTE is in MRIF mode?

[baimengwei]

In Chapter 4, there are the following sentences:
https://github.com/riscv-non-isa/riscv-iommu/blob/main/iommu_debug.adoc?plain=1#L13-L15

If the IOVA is determined to be that of a virtual interrupt file (Section 2.1.3.6) and the corresponding MSI PTE
 is in MRIF mode, then the process stops and reports a "Transaction type disallowed" (cause = 260) fault.

In Chapter 2.6, there are the following sentences:
https://github.com/riscv-non-isa/riscv-iommu/blob/main/iommu_data_structures.adoc?plain=1#L1262-L1264

If the translation request has an address determined to be an MSI address using the rules defined
by the Section 2.1.3.6 but the MSI PTE is configured in MRIF mode then a Success response is
generated with R, W, and U bit set to 1.

These two sentences seem to be contradictory, and why reports a "Transaction type disallowed" fault when the IOVA is determined to be that of a virtual interrupt file and the corresponding MSI PTE is in MRIF mode ?

If it should report a "Transaction type disallowed" fault when the IOVA is determined to be that of a virtual interrupt file and the corresponding MSI PTE is in MRIF mode, this condition might be part of the translation check in the chapter 2.3.3 which named "Process to translate addresses of MSIs".

[ved-rivos]

The debug interface is modeled similar to the ATS translation request interface. There is only a 64-bit register to return one address translation. MRIF mode translations need to return - notice interrupt ID, address of the notice MSI destination, and the address of the destination MRIF. That is why the debug interface does not support it.

[baimengwei]

The explanation is very clear, thank you.

[baimengwei]

Hi. sir

is the c model checks the msi pte in mrif mode which should report fault ? I can not find the matched code with the spec.

https://github.com/riscv-non-isa/riscv-iommu/blob/main/iommu_ref_model/libiommu/src/iommu_reg.c#L706

[ved-rivos]

Thanks for spotting that. That check was missing. Its now added by #447