[pve-devel] [PATCH qemu-server 1/2] Add USB3 support to Spice USB redirection

[Aaron Lauterer]

On 9/2/19 1:57 PM, Thomas Lamprecht wrote:
> On 8/30/19 9:40 AM, Aaron Lauterer wrote:
>> Signed-off-by: Aaron Lauterer <a.lauterer at proxmox.com>
>> ---
>>   PVE/QemuServer/USB.pm | 7 +++++--
>>   1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/PVE/QemuServer/USB.pm b/PVE/QemuServer/USB.pm
>> index a2097b9..05c78cf 100644
>> --- a/PVE/QemuServer/USB.pm
>> +++ b/PVE/QemuServer/USB.pm
>> @@ -87,9 +87,12 @@ sub get_usb_devices {
>>   	    my $hostdevice = parse_usb_device($d->{host});
>>   	    $hostdevice->{usb3} = $d->{usb3};
>>   	    if (defined($hostdevice->{spice}) && $hostdevice->{spice}) {
>> -		# usb redir support for spice, currently no usb3
>> +		# usb redir support for spice
>> +		my $bus = 'ehci';
>> +		$bus = 'xhci' if $hostdevice->{usb3};
>> +
>>   		push @$devices, '-chardev', "spicevmc,id=usbredirchardev$i,name=usbredir";
>> -		push @$devices, '-device', "usb-redir,chardev=usbredirchardev$i,id=usbredirdev$i,bus=ehci.0";
>> +		push @$devices, '-device', "usb-redir,chardev=usbredirchardev$i,id=usbredirdev$i,bus=$bus.0";
>>   	    } else {
>>   		push @$devices, '-device', print_usbdevice_full($conf, "usb$i", $hostdevice);
>>   	    }
>>
> 
> what the commit message does not mentions:
> 
> One could have set an usb3 spice variant already, e.g., with:
> # qm set 1000 --usb2 spice,usb3=1
> 
> and started it without issues, as we just ignored it.
> Now, with your patch it will suddenly change the backing bus to
> xhci, which (I assume) kills live migrations or restorations of
> snapshot with RAM.
> 
> So this would need to be guarded somehow, e.g., with a qemu
> machine version check.
> 

As described in the cover letter this is only true if other USB2 devices 
are added. Because only then will there be a "ehci.0" bus.

Otherwise the start of the VM will fail with this error: "Bus 'ehci.0' 
not found".

I did not think about the snapshot restore situation. I will integrate a 
qemu machine version check to handle it.