[libvirt] libvirt error while start vm with VGA passthrough

Daniel P. Berrange berrange at redhat.com
Thu Jan 31 13:40:18 UTC 2013


On Thu, Jan 31, 2013 at 09:29:52PM +0800, mzawdx wang wrote:
> http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Virtualization_Host_Configuration_and_Guest_Installation_Guide/chap-Virtualization_Host_Configuration_and_Guest_Installation_Guide-PCI_Assignment.html
> 
> I have followed the instructions in the RedHat reference
> above to the best of my ability to understand them.  I add
> the pci multi-port serial io card through virt-manager and
> it was indeed entered into the virtual machine's
> configuration file inside the <devices> tag:
> 
>     <hostdev mode='subsystem' type='pci' managed='yes'>
>       <source>
>         <address domain='0x0000' bus='0x00' slot='0x03'
> function='0x0'/>
>       </source>
>       <address type='pci' domain='0x0000' bus='0x00'
> slot='0x07' function='0x0'/>
>     </hostdev>
> 
> 
> However, when I try and start the virtual machine I get
> this error:
> 
> Error starting domain: internal error Unable to reset PCI
> device 0000:00:03.0: no FLR, PM reset or bus reset
> available

When assigning a PCI device to a guest, its state needs to
be reset. There are various ways to do this  - FLR or PM
reset are best because they can only affect the specific
device in question. If that's not possible, we have to
reset the entire PCI bus - this can only be done if all
devices on that bus are assigned to the same VM.

So the error message means your VGA card can't do FLR
or PM reset, and it is unsafe to do a bus reset due to
other devices on the same bus. So the only option is to
find out what other PCI devices are on the sme bus, and
assign them to the guest at the same time as the VGA
device.

This might be impossible if some of those devices are
required by your host, eg storage controller,  NIC, etc
In which case you're out of options.

Daniel
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