Re: [RFC KERNEL PATCH v4 3/3] PCI/sysfs: Add gsi sysfs for pci_dev

Bjorn Helgaas
2024-04-09T20:03:17Z

[+to Rafael]

On Mon, Apr 08, 2024 at 06:42:31AM +0000, Chen, Jiqian wrote:
> Hi Bjorn,
> It has been almost two months since we received your reply last time.
> This series are blocking on this patch, since there are patches on Xen and Qemu side depending on it.
> Do you still have any confusion about this patch? Or do you have other suggestions?
> If no, may I get your Reviewed-by?

- This is ACPI-specific, but exposes /sys/.../gsi for all systems,
including non-ACPI systems. I don't think we want that.

- Do you care about similar Xen configurations on non-ACPI systems?
If so, maybe the commit log could mention how you learn about PCI
INTx routing on them in case there's some way to unify this in the
future.

- Missing an update to Documentation/ABI/.

- A nit: I asked about s/dumU/DomU/ in the commit log earlier,
haven't seen any response.

- Commit log mentions "and for other potential scenarios." It's
another nit, but unless you have another concrete use for this,
that phrase is meaningless hand waving and should be dropped.

- A _PRT entry may refer directly to a GSI or to an interrupt link
device (PNP0C0F) that can be routed to one of several GSIs:

ACPI: PCI Interrupt Link [LNKA] (IRQs 3 4 5 6 7 9 10 *11 12 14 15)

I don't think the kernel reconfigures interrupt links after
enumeration, but if they are reconfigured at run-time (via _SRS),
the cached GSI will be wrong. I think setpnp could do this, but
that tool is dead. So maybe this isn't a concern anymore, but I
*would* like to get Rafael's take on this. If we don't care
enough, I think we should mention it in the commit log just in
case.

Bjorn