Re: [Xen-devel] VGA Passthrough crashes machine

[Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx>]

On Thu, Dec 15, 2011 at 03:54:00PM +0000, Anthony Wright wrote:
> On 14/12/2011 21:38, Konrad Rzeszutek Wilk wrote:
> > On Thu, Dec 08, 2011 at 12:00:07PM +0000, Anthony Wright wrote:
> >> I've just had my first attempt at getting VGA passthrough to work, and
> >> it crashed the machine. I'm trying to understand whether this is a
> >> problem with my hardware, configuration or a software problem.
> >>
> >> I'm running Xen 4.1.2 with Linux 3.1.2
> >>
> >>
> >> The CPU is an Intel Core i5-650
> >> http://ark.intel.com/products/43546/Intel-Core-i5-650-Processor-%284M-Cache-3_20-GHz%29
> > And what is your motherboard? Does it have VT-d?
> That was the important question... I'd missed the BIOS option to enable
> VT-d which was disabled by default. I enabled the BIOS option and
> everything worked, and it's very cool. :-)
> 
> This does beg a couple of other questions though....
> 
> Shouldn't I get a nice(ish) error message if I try to start a VGA
> passthrough VM on hardware that doesn't support it rather than crashing
> the machine?


There is this http://wiki.xen.org/xenwiki/VTdHowTo which gives you a
nice idea of what works.
> 
> Can I tell whether hardware will support VGA passthrough without trying
> to start a VM that uses it?
> 
> Also when I shut down the VM I have to use 'xl destroy' as I'm testing
> with Windows. After issuing the 'xl destroy' there is a long pause and
> then the error:
> 
>     libxl: error: libxl_device.c:470:libxl__wait_for_device_model Device
> Model not ready
>     libxl: error: libxl_pci.c:892:do_pci_remove Device Model didn't
> respond in time
> 
> If I pass through more than one device, I get the pause and the message
> for each device.

Hm, it looks to be sending 'pci-rem' to the XenStore, but I am not sure
if QEMU understands it. Did you compile Xen 4.1.2 by yourself? Did it
compile with CONFIG_PASSTHROUGH?

You should see some messages in the qemu.log about hot-remove and such.

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