Re: [Xen-users] Hiding PCI devices with modprobe.d

[Gordan Bobic <gordan@xxxxxxxxxx>]

On 17/06/2013 22:04, Daniel Shub wrote:
> I have now tried a number of different solutions for hiding the PCI devices, 
> but nothing is working completely. The simplest conceptually is David's 
> suggestion to load the xen-pciback module in the initrd. This guarantees that 
> the xen-pciback module gets loaded before any other modules have a chance to 
> bind the devices. This works nearly flawlessly, except for an issue with my 
> Intel integrated sound card that I am trying to hide. I am having the identical 
> problem as was discussed at 
> http://lists.xen.org/archives/html/xen-users/2013-05/msg00283.html where I need 
> to allow the dom0 to bind the sound card and load the kernel modules before 
> hiding it, otherwise I get noise and choppy playback in the domU. This means 
> Ian's suggestion of recompiling the kernel and and hiding the devices with grub 
> will likely not be any better.
>
> I then tried to hide the devices later since this would allow the dom0 to bind 
> the sound card. This is was basically a modification of Gordan's suggestion 
> where I unbind devices with a modprobe.d conf file since. My conf file is
>
>    install xen-pciback /root/pcidetach.sh; insmod /lib/modules/$(/bin/uname 
> -r)/kernel/drivers/xen/xen-pciback/xen-pciback.ko.gz
>
> where I tried a number of different things in pcidetach.sh. The problem I kept 
> running into is that I am running pcidetach.sh before loading the xen-pciback 
> module which means I cannot hide anything. i should say that Gordan's actual 
> suggestion probably would not run into this problem since he suggested 
> providing the configuration to prevent other modules from binding the devices.
Did you notice (or did I omit it...) that the first thing pcidetach.sh 
does is modprobe xen-pciback?
> I finally tried hiding the devices even later by creating a systemd udev service
>
>    [Unit]
>    Description=PCI hide
>
>    [Service]
>    Type=oneshot
>    ExecStart=/bin/bash /root/pcihide.sh
>
>    [Install]
>    WantedBy=multi-user.target
>
> where pcihide.sh uses the xl toolstack to hide the devices. This works, except 
> it runs after the domUs in /etc/xen/auto get started. I could obviously add the 
> start up of the domUs into pcihide.sh, but seems like a real hack.
>
> My plan is to go back to hiding the devices in the initrd where I load 
> explicitly load snd-intel-hda and then xen-pciback. I would need to create a 
> modprobe.d conf file that can handle unbinding the sound card similar to 
> Gordan's orginal suggestion. It is a little harder since I need to let it get 
> bound and then unbound before loading xen-pciback. I am still open to any 
> suggestions.
I guess the reason it works for me (I also use Intel ICH audio) is 
because I don't auto-start my VMs. I always start mine manually.
Gordan

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