Re: Updated MSI Patches

Jeff Garzik
2003-08-12T19:45:24Z

Zwane Mwaikambo wrote:
> On Tue, 12 Aug 2003, Jeff Garzik wrote:
>
>
>>So, IMO, do_IRQ is one special case where copying code may be preferred
>>over common code.
>>
>>And I also feel the same way about do_MSI(). However, I have not looked
>>at non-ia32 MSI implementations to know what sort of issues exist.
>
>
> The main reason i have a preference for a seperate MSI handling path is so
> that we don't have to do the platform_irq thing in do_IRQ and we know
> what to expect wrt irq or vector. If platform_irq stays we should at
> least try and pick up on what the IA64 folks have done, But that would be
> even harder to get done right now.

Oh, I definitely prefer a separate MSI handling path too.

In the future we'll be writing drivers that _require_ MSI interrupt
handling, and we'll be optimizing the various MSI hot paths to reclaim
even the most minute amount of CPU cycles. And we want to escape any
shackles the evil phrase "legacy interrupts" dares to try to lay upon us.

But there is a flip side to that: do_IRQ is not solely hardware
interrupts. That area of code is central dispatcher for
softirq/tasklet/timer delivery as well. So a separate do_MSI() needs to
take that stuff into account.

Overall, I'm pretty happy with how Tom's MSI patches are going so far,
and he seems to be responding to feedback. So, we'll get there.

Jeff