Re: [PATCH v2 0/3] PCI: endpoint: Support hardware-owned MSI-X table and PBA

[Niklas Cassel <cassel@kernel.org>]

On Wed, Sep 02, 2026 at 11:14:00AM +0900, Koichiro Den wrote:
> 
> This still sounds really odd, and it does not obviously explain why both DWORDs
> at 0x4000 and 0x4004 are affected. I may be missing something important. If
> anything similar involving iMSIX-TX Table RAM entry #0 has been discussed
> before, please point me to the relevant thread.
> 
> (Also, I can share my current WIP v3 series, which makes pci-epf-test and
> nvmet-pci-epf use the hardware-owned layout when available, while leaving
> pci-epf-ntb with its EPF-owned layout. If you have any setup where you could
> test it, please let me know.)

Some time ago, I did verify that I could raise an IRQ using
dw_pcie_ep_raise_msix_irq_doorbell(). If I remember correctly, I did so using
pci-epf-test and not nvmet-pci-epf.

Did pci-epf-test work? (From what you explain, it seems to be related to if
MSI-X Table entry #0 is used or not.)

Please share your branch. I should have time to do a quick test.


> 
> > 
> > 
> > What I suggest that you instead do something like:
> > Patch 1/7: pci-epf-vntb: Fix to actually use MSI-X when requested.
> >            This probably includes adding the code that is inside the
> > 	   if (ret == -ENOENT) { }.
> > Patch 2/7: PCI: endpoint: Support hardware-owned MSI-X table and PBA
> > Patch 3/7: PCI: dw-rockchip: Support fixed MSI-X table and PBA on RK3588
> > Patch 4/7: pci-epf-vntb: Add code that calls pci_epc_get_hw_msix_layout()
> >            and uses that layout, if the function returned success.
> > Patch 5/7: pci-epf-test: Add code that calls pci_epc_get_hw_msix_layout()
> >            and uses that layout, if the function returned success.
> > Patch 6/7: nvmet-pci-epf: Add code that calls pci_epc_get_hw_msix_layout()
> >            and uses that layout, if the function returned success.
> > Patch 7/7: pci-epf-ntb: Add comment that explains why it cannot call
> >            pci_epc_get_hw_msix_layout() like all other EPF drivers that
> > 	   support MSI-X.
> > 
> > 
> > This way, patch 1/7 can be backported, and will help all users vNTB users,
> > even the users that do not use RK3588 as an EPC.
> 
> That split makes sense. However, given the issue I described above, perhaps I
> should send patch 1/7 as a standalone fix and hold off on the rest until the
> issue is understood and resolved.

Agreed, a standalone 1/7 patch could be picked up without the need to wait for
any other changes.


> 
> Testing vNTB alone (ie. this v2 way) did not expose it because its first data
> doorbell uses MSI-X Table entry #2. I only found the issue because your
> suggestion led me to convert and test nvmet-pci-epf, thank you!

I'm sorry that we have a problem.
At least it is better to discover it now, rather than discovering it after
the patches had been merged.


Kind regards,
Niklas