Re: [patch 21/32] NTB/msi: Convert to msi_on_each_desc()

Jason Gunthorpe
2021-11-30T20:28:08Z

On Tue, Nov 30, 2021 at 08:48:03PM +0100, Thomas Gleixner wrote:
> Logan,
>
> On Tue, Nov 30 2021 at 12:21, Logan Gunthorpe wrote:
> > On 2021-11-29 5:29 p.m., Thomas Gleixner wrote:
> >> I'm way too tired to come up with a proper solution for that, but that
> >> PCI_IRQ_VIRTUAL has to die ASAP.
> >
> > I'm willing to volunteer a bit of my time to clean this up, but I'd need
> > a bit more direction on what a proper solution would look like. The MSI
> > domain code is far from well documented nor is it easy to understand.
>
> Fair enough. I'm struggling with finding time to document that properly.
>
> I've not yet made my mind up what the best way forward for this is, but
> I have a few ideas which I want to explore deeper.

I may have lost the plot in all of these patches, but I thought the
direction was moving toward the msi_domain_alloc_irqs() approach IDXD
demo'd here:

https://lore.kernel.org/kvm/162164243591.261970.3439987543338120797.stgit@djiang5-desk3.ch.intel.com/

I'd expect all the descriptor handling code in drivers/ntb/msi.c to
get wrapped in an irq_chip instead of inserting a single-use callback
to the pci core code's implementation:

void __pci_write_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
{
if (entry->write_msi_msg)
entry->write_msi_msg(entry, entry->write_msi_msg_data);

If this doesn't become an irq_chip what other way is there to properly
program the addr/data pair as drivers/ntb/msi.c is doing?

Jason