On 12/4/25 4:18 PM, Nam Cao wrote:

Hi Nilay,

Nilay Shroff [off-list ref] writes:

quoted

I have been using an NVMe disk on my PowerPC system that supports up to
129 MSI-X interrupt vectors. Everything worked fine until Linux kernel
v6.18, after which the NVMe driver stopped detecting the disk because
the driver probe now fails.

After further investigation, I found that the probe failure in v6.18
occurs during PCI/MSI-X vector allocation. A git bisect identified
commit daaa574aba6f (“powerpc/pseries/msi: Switch to msi_create_parent_
irq_domain()”) as the first bad commit.

Thanks for the report. I can (kind of) reproduce the problem with QEMU.

I think moving rtas_prepare_msi_irqs() into pseries_irq_domain_alloc()
should resolve the problem. But I'm not sure because I don't understand
how RTAS works.

Does IBM have some documentation describing the RTAS API? I failed to
google it.

Yes you can find the architecture document here: 
https://github.com/linuxppc/public-docs/blob/main/LoPAPR/LoPAR-20200812.pdf

You may refer section 7 in the above document, which describes RTAS API.

Thanks,--Nilay