Re: [Xen-devel] PCI and VGA Passthrough regressions on Xen 4.4.1 vs 4.3.2

[Zir Blazer <zir_blazer@xxxxxxxxxxx>]

Did some more experimentation. In this order:

0- Remade a Xen 4.4.1 package because I had deleted the previous one, both 
binary package and source. There could be some differences assuming that there 
were changes to the source repository, but I don't think so.

> [ 0.000000] xen:events: Using 2-level ABI | [ 0.000000] xen:events: Using 
> FIFO-based ABI
>
> Can you boot under Xen 4.4 Linux with 'xen.fifo=0' please?
> That should disable that (in case it is that)
>
> What kind of sounds issues is this? Is it poping with some
> rhytm or hissing ?

1- Adding iommu=verbose,debug in the Boot Loader config file as parameter for 
Xen. Gathered xl dmesg data from both Xen 4.3.2 and 4.4.1. All other test were 
exclusive to 4.4.1

2- Recorded sound from the DomU. To do so, I used the Windows XP Sound 
Recorder. In the global sound settings I used the Stereo Mixer as the Line In, 
then at the Control Panel in the Sound options there is a place that allows you 
to manually reproduce each of the Windows stock sounds. I reproduced the 
Windows starting sound and the closing one, twice each, while recording. The 
sound suffers from tons of quicks: Slowdowns, skippings, heavy and loud 
background noise and interference, etc.
If you want to reproduce the WAV, I suggest you to start with minimal volume, 
specially if you use headphones, unless you want to blow your ears. You've been 
warned.

2- Added xen.fifo=0 to the Boot Loader config file as parameter for the Linux 
Kernel. Gathered some more logs. Didn't fixed a thing.

3- Removed both xen.fifo and xen.pciback from Boot Loader config file. Used xl 
pci-assingnable-add 00.1b.0 to make the device available for DomU. Created the 
DomU. SUCCESS. Heavy logging of this one for obvious reasons. Dom0 should have 
just grabbed the Sound Card and initialized it with its Drivers. I don't have 
any means to reproduce sounds in Dom0, and can't hear any in case it does 
because default ALSA config has all channels muted, if I recall correctly.


So seems that the workaround than the guy I linked earlier works. I have to let 
Dom0 initialize the Sound Card. Because I didn't tested the VGA Passthrough, I 
don't know if this also work with it, but seems promising. Whatever it is, is 
something that Xen 4.4.1 does not do by its own but previously did. The funny 
thing is that there was also an issue with this at a previous Xen version, 
cause the guy I got the workaround idea from had issues with this back at 4.2 
two years ago, and for me it worked properly in both 4.3.1 and 4.3.2 but not 
4.4.1. No idea what could be the cause, but seems related to Xen version.


I didn't tested the hvmloader thing. Mind you tell me the usual route of that 
file? I have to make a copy of the one in the Xen 4.3.2 package, uninstall it, 
install Xen 4.4.1, and replace the hvmloader with the previous copy, right? If 
I do another go, I will test that and also VGA Passthrough.


Attached files are:

nastywindowssounds.wav  Broken passthrough sound. Put low volume before 
opening, it blows ears

Xen 4.3.2 with iommu=verbose,debug
syslinux-4.3.2-iommu.cfg        Boot Loader config
xl-dmesg-4.3.2-iommu.txt        xl dmesg output

Xen 4.4.1 with iommu=verbose,debug
syslinux-4.4.1-iommu.cfg        Boot Loader config
xl-dmesg-4.4.1-iommu.txt        xl dmesg output

Xen 4.4.1 with iommu=verbose,debug and Kernel with xen.fifo=0
syslinux-4.4.1-iommu-fifo.cfg   Boot Loader config
xl-dmesg-4.4.1-iommu-fifo.txt   xl dmesg output
dmesg-4.4.1-iommu-fifo.txt              dmesg output

Xen 4.4.1 with iommu=verbose,debug and NO xen.fifo or xen-pciback.hide 
syslinux-4.4.1-noxenpciback.cfg         Boot Loader config
xl-dmesg-4.4.1-noxenpciback.txt         xl dmesg output
dmesg-4.4.1-noxenpciback.txt            dmesg output
xl-info-4.4.1-noxenpciback.txt          xl info output
xl-v-create-4.4.1-noxenpciback.txt      xl -v create output (Hand made)
xl-wxp-4.4.1-noxenpciback.log           /var/log/xen file
qemu-dm-wxp-4.4.1-noxenpciback.log      /var/log/xen file

Attachment: xl-wxp-4.4.1-noxenpciback.log
Description: Text document

Attachment: xl-v-create-4.4.1-noxenpciback.txt
Description: Text document

Attachment: xl-info-4.4.1-noxenpciback.txt
Description: Text document

Attachment: xl-dmesg-4.4.1-noxenpciback.txt
Description: Text document

Attachment: xl-dmesg-4.4.1-iommu-fifo.txt
Description: Text document

Attachment: xl-dmesg-4.4.1-iommu.txt
Description: Text document

Attachment: xl-dmesg-4.3.2-iommu.txt
Description: Text document

Attachment: syslinux-4.4.1-noxenpciback.cfg
Description: Binary data

Attachment: syslinux-4.4.1-iommu-fifo.cfg
Description: Binary data

Attachment: syslinux-4.4.1-iommu.cfg
Description: Binary data

Attachment: syslinux-4.3.2-iommu.cfg
Description: Binary data

Attachment: qemu-dm-wxp-4.4.1-noxenpciback.log
Description: Text document

Attachment: dmesg-4.4.1-noxenpciback.txt
Description: Text document

Attachment: dmesg-4.4.1-iommu-fifo.txt
Description: Text document

Attachment: nastywindowssounds.wav
Description: Wave audio

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