Red Hat Bugzilla – Bug 436899
[DMAR] kernel panic with Intel(R) Core(TM)2 Duo CPU E6750
Last modified: 2009-12-31 05:53:32 EST
Description of problem:
The latest Fedora kernel 220.127.116.11-12.fc8 fails to boot with:
Kernel panic - not syncing: DMAR hardware is malfunctioning
This is on a HP Compaq desktop with CPU:
Intel(R) Core(TM)2 Duo CPU E6750 @ 2.66GHz
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Install latest Fedora 8 Kernel
Kernel panic at start of boot.
Boot to proceed as normal.
Boots with kernel 18.104.22.168-85.fc8 and earlier.
Same problem here, also with a E6750 @ 2.66Ghz (HP Workstation xw4600). Fedora 8
Does booting with the kernel option "intel_iommu=off" help?
Yes, the system boots with this setting, thank you!
The reporter of bug 436816 says a BIOS update fixed his problem.
Upgraded to bios v1.06, but no luck.
On a HP Compaq dc7800:
panics with latest kernel 22.214.171.124-34.fc8
boots with intel_iommu=off
bios is latest.
Also occurs on HP dc7800 with Intel Quad Core Q6600 on any kernel beyond
Need IOMMU for v.large memory operations within large simulations.
No BIOS upgrade available from HP. Where next??
(In reply to comment #7)
> Also occurs on HP dc7800 with Intel Quad Core Q6600 on any kernel beyond
> Need IOMMU for v.large memory operations within large simulations.
> No BIOS upgrade available from HP. Where next??
iommu=soft works. no significant degradation in memory ops to 8Gb. anticipate
no issue scaling upwards from there.
thanks for the setting. presume i can read up on all configs for iommu somewhere?
ideally, this box would boot without needing to specify options at all.
I'll send mail to some Intel folks and ask them to take a look at this.
(In reply to comment #9)
> iommu=soft works. no significant degradation in memory ops to 8Gb. anticipate
> no issue scaling upwards from there.
> thanks for the setting. presume i can read up on all configs for iommu somewhere?
In the kernel-doc package, files kernel-parameters.txt and x86_64/boot-options.txt
(I still don't understand why it panics the box if the hardware isn't working.
It should just fail the driver init and continue...)
*** This bug has been marked as a duplicate of 445553 ***
I encounter the same problem on my new netebook- hp compaq cq40 609tx...
I used the intel_iommu=off to start up installer...
It avoid the kernelpanic error, but stop on hardware detection at starting up installer...