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

On 2013-04-15 14:24, Gordan Bobic wrote:
> On 04/15/2013 01:02 PM, Peter Maloney wrote:
>> On 2013-04-15 10:32, Aurélien MILLIAT wrote:
>>>> 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).
That possibly depends on your distro... with openSUSE, I created my vms
with virt-manager, and then looked in /etc/xen and found a text version
and an xml one... so I deleted the xml ones, and hand edited the text ones.

Here is my very old working windows xp config:


You can just copy that wherever you want, and use it from the command
line and forget your old config.

vim /path/to/file
xm create /path/to/file
xm list
xm destroy nameofvm
xm destroy vmid

And FYI mine was 32 bit. I don't know if that matters.
> (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".
My guess is that attaching would work in windows to some extent .... but
my guess is that for non-plug and play OSses (windows is not truly plug
and play, even though they have claimed it was since windows 98), you
would have issues. So to be sure, you should have it in your config when
you "create" rather than attaching afterwards.

>> 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.
Well, if you have a cirrus card, I think that means it is definitely
secondary. Primary would remove the cirrus entirely. And yes, let's
focus on the config issue.
>>> 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.
I'm not sure about this ... I think we should make sure you have your
devices attached on the HVM "create" before we try to guess about this

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