Bug 1144582

Summary: After enabling IOMMU system hangs
Product: [Fedora] Fedora Reporter: iron-man
Component: kernelAssignee: Kernel Maintainer List <kernel-maint>
Status: CLOSED INSUFFICIENT_DATA QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: high Docs Contact:
Priority: unspecified    
Version: 20CC: gansalmon, iron-man, itamar, jonathan, kernel-maint, madhu.chinakonda, mchehab
Target Milestone: ---Flags: jforbes: needinfo?
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2014-12-10 15:01:42 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
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Description Flags
Current contets of /etc/default/grub
none
My lspci none

Description iron-man 2014-09-19 19:38:52 UTC
Created attachment 939416 [details]
Current contets of /etc/default/grub

Description of problem:
After explicitly enabling intel_iommu=on in the GRUB cmd line system hangs at the end of loading the X-window.

How reproducible:
always

Steps to Reproduce:
1.Append intel_iommu=on at the end of GRUB_CMDLINE_LINUX in /etc/default/grub
2.Execute grub2-mkconfig -o /boot/grub2/grub.cfg
3.Reboot the machine
4.When KDM login screen appears enter credentials
5.Wait until X finishes loading


Actual results:
System hangs immediately after X finishes loading. Sometimes it reaches the desktop. Only hard reboot and deleting the intel_iommu=on from boot parameters will make system to load properly.

Expected results:
Systems boot normally with Intel IOMMU support enabled for PCI passthrough to virtual machines in KVM.

Additional info:
My CPU (i7-4790) and MOBO (AsRock Z97 Extreme3) support Intel VT-d and it is enabled in BIOS.
When I boot into level 3 system works normally and "dmesg | grep -e IOMMU" shows that the Intel IOMMU is enabled. When I type "startx" the xwindow starts loading the KDE, and after it finishes the system hangs as previously described.

Comment 1 iron-man 2014-09-19 19:41:06 UTC
Created attachment 939417 [details]
My lspci

Comment 2 Justin M. Forbes 2014-11-13 16:02:20 UTC
*********** MASS BUG UPDATE **************

We apologize for the inconvenience.  There is a large number of bugs to go through and several of them have gone stale.  Due to this, we are doing a mass bug update across all of the Fedora 20 kernel bugs.

Fedora 20 has now been rebased to 3.17.2-200.fc20.  Please test this kernel update (or newer) and let us know if you issue has been resolved or if it is still present with the newer kernel.

If you have moved on to Fedora 21, and are still experiencing this issue, please change the version to Fedora 21.

If you experience different issues, please open a new bug report for those.

Comment 3 Justin M. Forbes 2014-12-10 15:01:42 UTC
This bug is being closed with INSUFFICIENT_DATA as there has not been a response in over 3 weeks. If you are still experiencing this issue, please reopen and attach the relevant data from the latest kernel you are running and any data that might have been requested previously.