Re: [PATCH 4/4] powerpc/eeh: Avoid event on passed PE

[Alexander Graf <agraf@suse.de>]

> Am 21.05.2014 um 02:19 schrieb Benjamin Herrenschmidt <benh@kernel.crashin=
g.org>:
>=20
>> On Tue, 2014-05-20 at 15:49 +0200, Alexander Graf wrote:
>> So how about we just implement this whole thing properly as irqfd?=20
>> Whether QEMU can actually do anything with the interrupt is a different=20=

>> question - we can leave it be for now. But we could model all the code=20=

>> with the assumption that it should either handle the error itself or=20
>> trigger and irqfd write.
>=20
> I don't object to the idea... however this smells of Deja Vu...
>=20
> You often tend to want to turn something submitted that fills a specific
> gap and implements a specific spec/function into some kind of idealized
> grand design :-) And that means nothing gets upstream for weeks or monthes=

> as we churn and churn...
>=20
> Sometimes it's probably worth it. Here I would argue against it and would
> advocate for doing the basic functionality first, as it is used by guests,=

> and later add the irqfd option. I don't see any emergency here and adding
> the irqfd will not cause fundamental design changes:
>=20
> The "passed" flag (though I'm not fan of the name) is really something
> we want in the low level handlers to avoid triggering host side EEH in
> various places, regardless of whether we use irqfd or not.
>=20
> This is totally orthogonal from the mechanism used for notifications.
>=20
> Even in host, the detection path doesn't always involve interrupts, and
> we can detect some things as a result of a host side config space access
> for example etc...
>=20
> So let's keep things nice and separate here. The interrupt notification
> is just an "optimization" which will speed up discovery of the error in
> *some* cases later on (but adds its own complexity since we have multiple
> discovery path in host, so we need to keep track whether we have notified
> yet or not etc...) so let's keep it for later.

EEH handling is your call, but I only see reduced complexity here. I won't n=
ak the current approach though.


Alex