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

[Vivian Wang <wangruikang@iscas.ac.cn>]

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.

> 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.

Thanks again,
Vivian "dramforever" Wang

> Fixes: 386ced19e9a3 ("PCI/MSI: Convert the boolean no_64bit_msi flag to a DMA address mask")
> Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
> ---
>  arch/powerpc/kernel/pci_of_scan.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> [...]