Re: [PATCH] powerpc/pci: Initialize msi_addr_mask for OF-created PCI devices

[Nilay Shroff <nilay@linux.ibm.com>]

On 2/19/26 12:52 PM, Vivian Wang wrote:
> On 2/18/26 01:45, Nilay Shroff wrote:
> 
>> Recent changes [1] replaced the use of no_64bit_msi with msi_addr_mask.
>> As a result, msi_addr_mask is now expected to be initialized to
>> DMA_BIT_MASK(64) when a pci_dev is set up. However, this initialization
>> was missed on powerpc due to differences in the device initialization
>> path compared to other architectures. Due to this, now pci device probe
>> method fails on powerpc system.
>>
>> On powerpc systems, struct pci_dev instances are created from device
>> tree nodes via of_create_pci_dev(). Because msi_addr_mask was not
>> initialized there, it remained zero. Later, during MSI setup,
>> msi_verify_entries() validates the programmed MSI address against
>> pdev->msi_addr_mask. Since the mask was not set correctly, the
>> validation fails, causing PCI driver probe failures for devices on
>> powerpc systems.
> 
> Thanks for catching this. I had naively assumed that pci_setup_device()
> was the right place for adding this initialization, and didn't think of
> other possibilities.
> 
> I grep'd for pci_alloc_dev() and found these uses:
> 
>   * of_create_pci_dev() in arch/powerpc/kernel/pci_of_scan.c (this patch)
>   * of_create_pci_dev() in arch/sparc/kernel/pci.c (*same missed init*)
>   * drivers/char/agp/{alpha,parisc}-agp.c (fake pci_dev, should be fine)
>   * drivers/scsi/megaraid.c (copying from existing pci_dev, should be fine)
> 
> So, while we're at it, can we fix the SPARC one as well in v2? The code
> seems similar to what we do for powerpc.

Yes I can do that but I don't have access to SPARC machine so I can't validate 
it. However I'd add SPARC maintainers and mailing list for review and so someone
might help.

> 
>> Initialize pdev->msi_addr_mask to DMA_BIT_MASK(64) in
>> of_create_pci_dev() so that MSI address validation succeeds and device
>> probe works as expected.
>>
>> [1] https://lore.kernel.org/all/20260129-pci-msi-addr-mask-v4-0-70da998f2750@iscas.ac.cn/
> 
> Nit: Link seems redundant given the Fixes tag below.
> 
Ack

Thanks,
--Nilay