linux-kernel - Re: i915-related and general system freezes with specific kernel config // IOMMU

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Date:	Sat, 19 Jan 2013 17:13:14 +0100
From:	Mihai Moldovan <ionic@...ic.de>
To:	Daniel Vetter <daniel.vetter@...ll.ch>
CC:	LKML <linux-kernel@...r.kernel.org>,
	David Woodhouse <dwmw2@...radead.org>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: i915-related and general system freezes with specific kernel
 config // IOMMU

* On 19.01.2013 02:27 PM, Daniel Vetter wrote:
> You have a gen4.5 chipset which is known to be utterly broken for
> IOMMU+intel gpu.

Nice description for what I'm seeing. ;)

After some more hours of uptime I'm inclined to say, that "intel_iommu=off
iommu=off" fixes my random freezes as well.
Alas, the USB and PCI(e) problems are still around, but I could test recompiling
3.7.2 with Intel IOMMU turned off completely in the kernel config.
Interestingly, my 3.0.2 kernel which worked fine for so long doesn't even *have*
support for VT-d/Intel IOMMU. This could explain why I wasn't bit by those
problems on all previous versions.

> [...] and we've never added the proper
> quirks. See https://bugzilla.kernel.org/show_bug.cgi?id=51921 for a
> proposed patch to fix this (i.e. automatically set
> intel_iommu=igfx_off for affected platfroms). Testing highly welcome.

From a quick glance, I don't think this patch will work as-is, my PCI ID 2e12 is
missing.
I'll add it to the relevant section.

But even if it worked, I'd still have the "box freezes randomly" issue (mostly
within 5 to 60 minutes of uptime). :(
The only way to get rid of this is disabling Intel IOMMU as a whole via kernel
parameters intel_iommu=off iommu=off.

Anyway, I'll give it a try.

Best regards,

Mihai

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