Re: [RFC] I/O MCA recovery

David Mosberger
2004-05-04T22:51:38Z

>>>>> On Tue, 4 May 2004 15:36:13 -0700, Jesse Barnes <jbarnes@engr.sgi.com> said:

>> User-level accesses are mapped via the MMU so you could always
>> intercept the page-faults.

Jesse> Wouldn't that mean that on every I/O access we'd have to page
Jesse> fault, do the I/O, and then invalidate the mapping? That
Jesse> seems like a lot of overhead.

Yes. I doubt it would be an issue for inX/outX emulation in the int10
module.

Jesse> Also, with this scheme, we could potentially recover from
Jesse> regular read/writes too.

>> _If_ there is an infrastructure what you can hook into, fine.
>> But I'm highly suspicious of using broken platforms as a
>> justification for new infrastructure.

Jesse> Are you describing ia64 as a broken platform here?

Hardly.

Jesse> The problem I'm trying to solve isn't sn2 specific (though
Jesse> part of the X stuff I have to do will be driven by sn2
Jesse> requirements)

I was talking about hard-failure of inX/outX. If SN2 does that, it's
broken and I'm not terribly sympathetic (but see below).

Jesse> it's a generic way to deal with hard fails on PIO reads,
Jesse> which afaik, affects all ia64 platforms. Correct me if I'm
Jesse> wrong here...

Let me try to say it differently: inX/outX must soft-fail. How you
achieve that on SN2, I don't really care. If, for other reasons,
there happens to be an infrastructure you can hook into to facility
implementation of soft-fail inX/outX on SN2, that's certainly fine by
me. But don't try to use inX/outX soft-fail as a reason to justify
the infrastructure. Better?

--david