Re: [RFC PATCH 2/3] PCI/MSI: Implement irq_mask_nowait() for MSI-x

[Keith Busch <kbusch@kernel.org>]

On Wed, Oct 14, 2026 at 11:10:45PM +0200, Thomas Gleixner wrote:
> On Wed, Oct 14 2026 at 12:31, Bjorn Helgaas wrote:
> >> Skip the read-back that flushes the MSI-x mask write. Parent domains
> >> that mask on behalf of PCI/MSI continue using their own irq_mask().
> >> 
> >> Signed-off-by: Keith Busch <kbusch@kernel.org>
> >
> > I assume Thomas will review/ack the pci/msi/ parts.
> 
> Yes. I actually suggested that "nowait" mechanism to Keith at LPC.
> 
> Though I hate the name of that callback because irq_mask() does not
> really wait. It guarantees that the mask store has reached the device
> which means that after that point no further interrupts will be sent by
> the device (assuming sane hardware). That means it's a synchronous
> operation which involves flushing the store, so maybe irq_mask_noflush()
> or irq_mask_async() might be more accurate and descriptive.

Right thank you, I misremembered your suggested name. I am totally fine
with "noflush", and I've made that change in my local branch. I'll just
wait a bit for any other feedback before the next version.

> > Cc'd Luigi since I know he's interested in interrupt moderation in
> > general.
> 
> Correct. I'm curious whether the interrupt frequency based moderation
> mechanism Luigi is proposing does solve the NVME issues as well or can
> be combined with some device specific hint mechanism.
> 
> That said, Luigi's approach should benefit from the "nowait" mechanism
> as well.
> 
> Luigi?
> 
> Thanks,
> 
>         tglx