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

[Thomas Gleixner <tglx@kernel.org>]

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.

> 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