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[Bug 1428121] Re: Intel HDMI Audio not working with IOMMU enabled


Status changed to 'Confirmed' because the bug affects multiple users.

** Changed in: alsa-driver (Ubuntu)
       Status: New => Confirmed

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  Intel HDMI Audio not working with IOMMU enabled

Status in alsa-driver package in Ubuntu:

Bug description:
  New ASRock Z97 Extreme 6 motherboard with an Intel i7 4790S and an
  Nvidia GTX 650.

  Host uses Intel IGD for video and HDMI audio out.

  When I pass kernel flags 'intel_iommu=on' or 'intel_iommu=on,igfx_on'
  HDMI audio no longer functions although the device and modules seem to
  load and I cannot locate any error messages.  In this configuration
  IOMMU functions as expected and I can successfully pass the Nvidia
  card through to a KVM guest using VFIO.

  As per this
  (https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1223840) bug
  report and the linked bugzilla thread I attempted to use kernel flag
  'intel_iommu=on,igfx_off'.  This resolves the HDMI audio out but
  breaks IOMMU as in VGA pass through generates DMA errors.

  I'm running from a clean installation of 14.10 with no modifications
  to the kernel or kvm, qemu, libvirt or virt-manager.

  In either scenario above the analogue audio out continues to function,
  I haven't tested the optical out as I have no hardware to do so.

  ProblemType: Bug
  DistroRelease: Ubuntu 14.10
  Package: linux-image-3.16.0-31-generic 3.16.0-31.41
  ProcVersionSignature: Ubuntu 3.16.0-31.41-generic 3.16.7-ckt5
  Uname: Linux 3.16.0-31-generic x86_64
  ApportVersion: 2.14.7-0ubuntu8.2
  Architecture: amd64
   /dev/snd/controlC2:  kelvin     3468 F.... pulseaudio
   /dev/snd/controlC3:  kelvin     3468 F.... pulseaudio
   /dev/snd/controlC0:  kelvin     3468 F.... pulseaudio
   /dev/snd/controlC1:  kelvin     3468 F.... pulseaudio
  CurrentDesktop: Unity
  Date: Wed Mar  4 12:53:17 2015
  HibernationDevice: RESUME=UUID=4d35060a-85c4-45fd-9f8e-530491588931
  InstallationDate: Installed on 2015-02-26 (5 days ago)
  InstallationMedia: Ubuntu-Server 14.10 "Utopic Unicorn" - Release amd64 (20141022.2)
  MachineType: To Be Filled By O.E.M. To Be Filled By O.E.M.
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.16.0-31-generic.efi.signed root=UUID=4914f227-6bb0-40bb-a781-9ad7111a996f ro intremap=no_x2apic_optout intel_iommu=on,forcedac pci-stub.ids=10de:11c8,10de:0e0b nomdmonddf nomdmonisw
   linux-restricted-modules-3.16.0-31-generic N/A
   linux-backports-modules-3.16.0-31-generic  N/A
   linux-firmware                             1.138.1
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 12/17/2014
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: P1.70
  dmi.board.name: Z97 Extreme6
  dmi.board.vendor: ASRock
  dmi.chassis.asset.tag: To Be Filled By O.E.M.
  dmi.chassis.type: 3
  dmi.chassis.vendor: To Be Filled By O.E.M.
  dmi.chassis.version: To Be Filled By O.E.M.
  dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrP1.70:bd12/17/2014:svnToBeFilledByO.E.M.:pnToBeFilledByO.E.M.:pvrToBeFilledByO.E.M.:rvnASRock:rnZ97Extreme6:rvr:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
  dmi.product.name: To Be Filled By O.E.M.
  dmi.product.version: To Be Filled By O.E.M.
  dmi.sys.vendor: To Be Filled By O.E.M.

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