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

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Message-ID: <20130402161757.GC17519@pd.tnic>
Date:	Tue, 2 Apr 2013 18:17:57 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Joerg Roedel <joro@...tes.org>
Cc:	suravee.suthikulpanit@....com, iommu@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] iommu/amd: Add logic to decode AMD IOMMU event flag

On Tue, Apr 02, 2013 at 06:04:00PM +0200, Joerg Roedel wrote:
> I can certainly write a patch that works around your particular BIOS
> bug. The problem is that such a fix will most certainly break other
> systems.
>
> Unfortunatly there is no reliable way to fixup the IO-APIC-ID->DEVID
> mapping at runtime when the BIOS messed it up. The only thing I can do
> is to check for potential problems and disable the intremap feature
> then, so that the system will at least boot.

Yeah, that could work:

* do not issue message but try to fixup the mapping
* if it works, fine
* if it doesn't, then give up and disable intremap.

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.

-- 
Regards/Gruss,
    Boris.

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