Hi, I'm running Xen hypervisor and using PCI passthrough to assign an Intel HDA audio device (00:1f.3 Audio device: Intel Corporation Cannon Point-LP High Definition Audio Controller (rev 30)) to a Xen HVM virtual machine. I do this for both Linux 5.4.185 and a different Windows 10 VM (only one at a time). The Windows VM seems to work every time. The Linux VM has issues after the first VM boot. This is one boot of the physical hardware and multiple boots of the virtual machines. For Linux, on first boot, the sound card is detected and works properly. After that, things usually don't work. I just ran a reboot loop and it was: 1st boot - audio detected and working 2 & 3 - no audio 4th - audio detected and working 5 - 20 - no audio For boots 2, 3, 5-7, dmesg shows: [ 0.760401] hdaudio hdaudioC0D0: no AFG or MFG node found [ 0.760415] snd_hda_intel 0000:00:06.0: no codecs initialized For boots 8+, the errors changed to: [ 0.783397] hdaudio hdaudioC0D0: cannot read sub nodes for FG 0x10 [ 0.783413] snd_hda_intel 0000:00:06.0: no codecs initialized At this point, I booted a Windows 10 VM and audio works Trying to boot Linux again gives a new error message [ 0.789041] snd_hda_intel 0000:00:06.0: Unknown capability 0 [ 1.811205] snd_hda_intel 0000:00:06.0: No response from codec, resetting bus: last cmd=0x0eef0004 [ 1.811246] hdaudio hdaudioC0D0: cannot read sub nodes for FG 0x10ee [ 1.811263] snd_hda_intel 0000:00:06.0: no codecs initialized Reboot VM and it's back to: [ 0.775917] hdaudio hdaudioC0D0: no AFG or MFG node found [ 0.775932] snd_hda_intel 0000:00:06.0: no codecs initialized Reboot VM and again: [ 0.789069] hdaudio hdaudioC0D0: cannot read sub nodes for FG 0x10 [ 0.789084] snd_hda_intel 0000:00:06.0: no codecs initialized Reboot physical laptop: 1. boot Windows 10 - audio works 2. boot Linux - audio works 3. reboot Linux - no audio [ 0.773111] hdaudio hdaudioC0D0: no AFG or MFG node found [ 0.773151] snd_hda_intel 0000:00:06.0: no codecs initialized This seems to me like Windows does a better job resetting the card to get the audio hardware working. Any suggestions on what to investigate? Thanks, Jason
