Re: [Xen-users] ATI VGA Passthrough / Xen 4.2 / Linux 3.8.6

[Gordan Bobic <gordan@xxxxxxxxxx>]

On 04/15/2013 01:02 PM, Peter Maloney wrote:
> On 2013-04-15 10:32, Aurélien MILLIAT wrote:
> > > De : xen-users-bounces@xxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxx] 
> > > De la part de Gordan Bobic
> > > Envoyé : lundi 15 avril 2013 00:47
> > > À : xen-users@xxxxxxxxxxxxx
> > > Objet : [Xen-users] ATI VGA Passthrough / Xen 4.2 / Linux 3.8.6
> > >
> > > Hi,
> > >
> > > I'm trying to get VGA passthrough to work to an XP x64 guest, and I'm seeing 
> > > "interesting" things happening.
> > >
> > > I'm using the kernel and userspace tools from here:
> > > http://xen.crc.id.au/support/guides/install/#
> > > on Scientific Linux 6.
> > >
> > > I gave up on trying to get an Nvidia card to work in the guest having read 
> > > about the extra patches required to get a non-Quadro card to work.
> > > So I switched to using an ATI 6450/7450 card. This works fine - almost.
> > > ATI cards have a secondary audio output device function on them for outputting audio 
> > > over HDMI outputs. When I pass both the VGA and >the HDMI audio devices from the 
> > > host to the guest, the guest cannot use the VGA card. It always shows up as unusable 
> > > in the guest (yellow >exclamation mark in XP x64).
> I had this problem (windows XP only), and fixed it by setting:
>
> stdvga=1
That's another thing I've been meaning to ask - where are the VM configs 
stored? I am using xend with VMs configured using virt-manager on EL6, 
and I cannot figure out where it put the configuration. It doesn't 
appear to be in /etc/xen. So where is it and how do I get to it? I ask 
because virt-manager doesn't actually show a Video adapter in the 
configuration after the VM is created (a bug no doubt).
(Yes, I know virt-manager is a pile of crap, and won't even let me 
attach the PCI devices, I have to do it using "xm pci-attach", after 
which it sees they are attached - but it's all I have to work with at 
the moment - OpenXenManager locks up on me as soon as it tried (and 
fails) to authenticate. Are there any other recommendable Linux tools 
for managing and configuring Xen VMs?)
Also, with the ATI card passed through as a normal PCI device, once it 
is picked up by the OS and the driver is installed, the cirrus card no 
longer works - yellow exclamation mark in device manager, and the only 
video output is from the ATI card.
While convenient, I'm not sure this is "normal".

> Which means something like: replace the cirrus logic emulated card with
> a stdvga emulated card.
>
> And then I guess what happens is: winxp is too old to understand the new
> card ;) and has to fall back to the passed through one, and somehow that
> makes it work, maybe because it initializes it differently during boot
> up (when starting the AMD graphics driver).
>
> Also, make sure you have already installed the AMD graphics drivers in XP.
Without the ATI drivers (or in safe mode) only the Cirrus card comes up. 
In normal mode with ATI drivers only the ATI card comes up.
> And be sure you set gfx_passthrough=0 (secondary passthrough, with AMD
> support) rather than =1 (primary passthrough, without AMD support)
See above - I need to find the configs first. Can you point me in the 
right direction? I figured it must be in xenstored or something, but 
googling about it didn't prove conclusive.
> > I've got the same behavior with Quadro FX3800. One possible workaround for that 
> > is to deactivate then to activate the card in your domU and reboot it.
> > Check if you have FLR function (lspci -vv): 
> > http://wiki.xen.org/wiki/Xen_PCI_Passthrough#How_can_I_check_if_PCI_device_supports_FLR_.28Function_Level_Reset.29_.3F
> > I think this behavior is linked to the non-support of this function.
> The patches AMD sent the xen devs, plus the passthrough support in the
> driver, are supposed to handle this lack of FLR.
Speaking of which - is there a way to force the device reset? I'm 
finding that sometimes all I get from the VM is a blank screen, after 
the monitor flickers briefly. The emulated VGA card shows nothing after 
the low level startup, and the desktop/login which is expected to come 
up on the VGA card - doesn't. I haven't yet figured out if there is a 
specific chain of actions that leads to this, so any pointers on where 
to look would be welcome.
Gordan

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