Re: [PATCH 1/3] iommu/amd: Add logic to decode AMD IOMMU event flag

[Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>]

On Tue, Apr 02, 2013 at 06:33:18PM +0200, Joerg Roedel wrote:
> I can't find out in the driver whether the fix works or not. It will
> be noticed later when the x86 code tries to setup the timers and finds
> out that they don't work, which causes a kernel panic.
>
> Okay, in theory I could implement a feedback loop between timer-setup
> and intremap code and try fixups until it works. But that seems not to
> be worth it to work around a buggy BIOS.

Yeah, same here. It's not like we really need intremap to work - we're
only trying to fix the annoying error message currently. :-)

> What I actually thought about was providing an IVRS-override on the
> kernel command line. So that you can specify the IOAPIC_ID->DEVID
> mapping there and make it work this way. What do you think?

I guess that is workable. I can imagine people wanting this if they want
to do the intremap thing on such b0rked BIOSen. So how do I specify this
IOAPIC_ID->DEVID mapping on the cmdline exactly?

> > And yes, I'm very sceptical about having a WARN_ON and it starts
> > screaming on machines all over the place. Good luck explaining to
> > people that you actually wanted to prod BIOS vendors to fix their
> > monkey-on-crack code but they weren't listening in the first place.
> 
> Yeah, that's my fear too. So we leave it better as it is...

Hohumm.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
--