Re: [PATCH v9 7/7] PCI: endpoint: pci-ep-msi: Add embedded doorbell fallback

[Niklas Cassel <cassel@kernel.org>]

On Sat, Feb 21, 2026 at 02:42:35AM +0900, Koichiro Den wrote:
> On second thought, I'm wondering whether it makes sense to handle the case where
> the embedded doorbell target resides behind an IOMMU in this series.
> 
> In v9, we simply expose the raw physical address without establishing an IOMMU
> mapping. When the EPC parent device is attached to an IOMMU domain, a Host->EP
> MMIO write through the BAR window may result in an IOMMU fault.
> 
> Initially, I planned to submit IOMMU support separately as a follow-up series
> once this series is accepted, to avoid making this series too large [1].
>
> Niklas, any comments would be appreciated.

These patches are for NTB/vNTB:

> [1] Supporting such an IOMMU-backed case would likely require additional
>     patches for vNTB + ntb_transport to demonstrate usability, such as:
>     https://lore.kernel.org/all/20260118135440.1958279-12-den@valinux.co.jp/
>     https://lore.kernel.org/all/20260118135440.1958279-16-den@valinux.co.jp/
>     https://lore.kernel.org/all/20260118135440.1958279-19-den@valinux.co.jp/

If the diff you pasted above is all you need for pci-epf-test to pass the
doorbell test case when running against a PCI endpoint with IOMMU enabled,
then I suggest you just send a v10 with those changes included, without
any additional dependencies.

I understand that you would need additional dependencies for vNTB to be able
to use eDMA doorbell on a PCI endpoint with IOMMU enabled.

Perhaps, drop the vNTB changes from this series, focus only on pci-epf-test,
get this series merged, and then submit an follow up series that adds eDMA
doorbells with IOMMU support for vNTB?


Kind regards,
Niklas