Re: [PATCH] PCI: dwc: ep: Fix regression in dw_pcie_ep_raise_msi_irq()

[Niklas Cassel <cassel@kernel.org>]

On Wed, Feb 25, 2026 at 02:05:53PM -0600, Bjorn Helgaas wrote:
> On Tue, Feb 10, 2026 at 07:12:25PM +0100, Niklas Cassel wrote:
> 
> I put this on pci/for-linus for v7.0, thanks!
> 
> I'd like to make the commit log a little more general, since the issue
> affects any endpoint driver.  Here's my proposal; I'll update it based
> on your feedback:
> 
>   PCI: dwc: ep: Fix dw_pcie_ep_raise_msi_irq() Message Address cache
> 
>   Endpoint drivers use dw_pcie_ep_raise_msi_irq() to raise MSI interrupts to
>   the host.  After 8719c64e76bf ("PCI: dwc: ep: Cache MSI outbound iATU
>   mapping"), dw_pcie_ep_raise_msi_irq() caches the Message Address from the
>   MSI Capability in ep->msi_msg_addr.  But that Message Address is controlled
>   by the host, and it may change.  For example, if:
> 
>     - firmware on the host configures the Message Address and triggers an
>       MSI,
> 
>     - a driver on the Endpoint raises the MSI via dw_pcie_ep_raise_msi_irq(),
>       which caches the Message Address,
> 
>     - a kernel on the host reconfigures the Message Address and the host
>       kernel driver triggers another MSI,
> 
>   dw_pcie_ep_raise_msi_irq() notices that the Message Address no longer
>   matches the cached ep->msi_msg_addr, warns about it, and returns error
>   instead of raising the MSI.  The host kernel may hang because it never
>   receives the MSI.
> 
>   This was seen with the nvmet_pci_epf_driver: the host UEFI performs NVMe
>   commands, e.g. Identify Controller to get the name of the controller,
>   nvmet-pci-epf posts the completion queue entry and raises an IRQ using
>   dw_pcie_ep_raise_msi_irq().  When the host boots Linux, we see a
>   WARN_ON_ONCE() from dw_pcie_ep_raise_msi_irq(), and the host kernel hangs
>   because the nvme driver never gets an IRQ.
> 
>   Remove the warning when dw_pcie_ep_raise_msi_irq() notices that Message
>   Address has changed, remap using the new address, and update the
>   ep->msi_msg_addr cache.

Looks good to me!

You've been reviewing/discussing the patch already, so you were already
very familiar with the problem. Thank you for picking it up!


Kind regards,
Niklas