Kernel panic on Linux 4.1 with intel_iommu=on

Kernel panic on Linux 4.1 with intel_iommu=on

[Ting-Wei Lan]

Hardware:
Intel Core i5 CPU 650 @ 3.20GHz
Intel Ironlake Desktop

In order to use VT-d on this computer, I have to use 'intel_iommu=on
intel_iommu=igfx_off' to prevent graphics problems and system crash.
This problem happens on Linux 3.7 and later versions, including the
latest release, Linux 4.1.

I found Intel-IOMMU.txt says I should file a bug if
intel_iommu=igfx_off fixes anything. I filed the bug on freedesktop ->
DRI -> DRM/Intel.
https://bugs.freedesktop.org/show_bug.cgi?id=91127

After I applied this patch, I no longer saw graphics problems, and Xorg
and Wayland can be successfully started without intel_iommu=igfx_off.
https://bugs.freedesktop.org/show_bug.cgi?id=91127#c6

However, after using the system for about one hour, the system crashed
and printed some messages on the serial console. I have to press the
reset button to reboot the machine.
https://bugs.freedesktop.org/show_bug.cgi?id=91127#c8

Can anyone here help us resolve this problem?

Re: Kernel panic on Linux 4.1 with intel_iommu=on

[Ting-Wei Lan]

於 三，2015-07-01 於 03:32 +0800，Ting-Wei Lan 提到：
> Hardware:
> Intel Core i5 CPU 650 @ 3.20GHz
> Intel Ironlake Desktop
> 
> In order to use VT-d on this computer, I have to use 'intel_iommu=on
> intel_iommu=igfx_off' to prevent graphics problems and system crash.
> This problem happens on Linux 3.7 and later versions, including the
> latest release, Linux 4.1.
> 
> I found Intel-IOMMU.txt says I should file a bug if
> intel_iommu=igfx_off fixes anything. I filed the bug on freedesktop 
> ->
> DRI -> DRM/Intel.
> https://bugs.freedesktop.org/show_bug.cgi?id=91127
> 
> After I applied this patch, I no longer saw graphics problems, and 
> Xorg
> and Wayland can be successfully started without intel_iommu=igfx_off.
> https://bugs.freedesktop.org/show_bug.cgi?id=91127#c6

The patch was merged in Linux 4.2-rc2.
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/
?id=8b572a4

> 
> However, after using the system for about one hour, the system 
> crashed
> and printed some messages on the serial console. I have to press the
> reset button to reboot the machine.
> https://bugs.freedesktop.org/show_bug.cgi?id=91127#c8

I have upgraded my system to Linux 4.2-rc2, and I can reproduce the
problem on it. Here is the full dmesg log:
https://bugs.freedesktop.org/attachment.cgi?id=117170

Can anyone here help us resolve this problem?
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