Re: [pve-devel] [PATCH qemu-server v1 1/2] virtio-vga-gl: add Vulkan (venus) support

[Markus Frank <m.frank@proxmox.com>]

On 2025-11-10 15:27, Thomas Lamprecht wrote:
> Am 10.11.25 um 12:40 schrieb Markus Frank:
>> The venus protocol facilitates the translation of Vulkan API calls via
>> the virglrenderer. To use it, the virgl-server package must be installed
>> on the host.
>>
>> The Vulkan option is represented by an enum with values such as
>> 'venus-512' and 'venus-1024'. This is to allow for the potential
>> addition of another Vulkan implementation in the future. The number
>> indicates the memory window in MiB for Venus.
> 
> Meh, if it provides no obvious benefit I'm not sure if this makes sense
> to add now already.
> 
> I'd also mention more prominently that this only works for the virtio-gl
> type, at least in the commit message and probably also in the description
> of the vulkan "flag".
> Is this strongly limited to that display type? And are there errors
> generated with others combination that block the start?

Yes, it is limited to virtio-gl. I will update the description.
It should also mention that 'virgl-server' needs to be installed on the host.

And yes, there is an error. See inline below.

> Asking mostly to see if it would be an option to just generate a log_warn
> about a useless combination of display and venus that then shows up in the
> start task in such a case.
> 
> And is it likely that there might be another protocol that relays vulkan?

A different protocol already exists for Vulkan: virtio-gpu rutabaga [1].
However, I do not think this one is really suitable for PVE.
I would not rule out the possibility of another implementation in the future.

[1] https://www.qemu.org/docs/master/system/devices/virtio/virtio-gpu.html#virtio-gpu-rutabaga

> 
> Mostly asking this key questions to better judge the design/approach you
> chose.
> 
>>
>> Signed-off-by: Markus Frank <m.frank@proxmox.com>
>> ---
>>   src/PVE/QemuServer.pm | 20 +++++++++++++++++++-
>>   1 file changed, 19 insertions(+), 1 deletion(-)
>>
>> diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
>> index cf195ccc..2b358e9f 100644
>> --- a/src/PVE/QemuServer.pm
>> +++ b/src/PVE/QemuServer.pm
>> @@ -160,6 +160,12 @@ my $vga_fmt = {
>>               qw(cirrus qxl qxl2 qxl3 qxl4 none serial0 serial1 serial2 serial3 std virtio virtio-gl vmware)
>>           ],
>>       },
>> +    vulkan => {
>> +        description => 'Enable vulkan by using the venus protocol.',
>> +        type => 'string',
>> +        enum => ['venus-512', 'venus-1024', 'venus-2048', 'venus-4096', 'venus-8192'],
>> +        optional => 1,
>> +    },
>>       memory => {
>>           description => "Sets the VGA memory (in MiB). Has no effect with serial display.",
>>           type => 'integer',
>> @@ -1499,6 +1505,15 @@ sub print_vga_device {
>>           $pciaddr = print_pci_addr($vgaid, $bridges, $arch);
>>       }
>>   
>> +    my $venus = "";
>> +    if ($vga->{vulkan} && $vga->{vulkan} =~ /^venus-(\d+)/) {
>> +        my $virgl_memory_window = $1;
>> +        $venus = ",hostmem=${virgl_memory_window}M,venus=on,blob=on";
>> +
>> +        die "You need to use virtio-gl to enable vulkan (venus) support!\n"
>> +            if $vga->{type} !~ /^virtio-gl/;
>> +    }

Here is a die to prevent starting without virtio-gl.

>> +
>>       if ($vga->{type} eq 'virtio-gl') {
>>           my $base = '/usr/lib/x86_64-linux-gnu/lib';
>>           die "missing libraries for '$vga->{type}' detected! Please install 'libgl1' and 'libegl1'\n"
>> @@ -1507,9 +1522,12 @@ sub print_vga_device {
>>           die
>>               "no DRM render node detected (/dev/dri/renderD*), no GPU? - needed for '$vga->{type}' display\n"
>>               if !PVE::Tools::dir_glob_regex('/dev/dri/', "renderD.*");
>> +
>> +        die "missing virgl render server for vulkan (venus)! Please install 'virgl-server'.\n"
>> +            if $vga->{vulkan} && !-e "/usr/libexec/virgl_render_server";
>>       }
>>   
>> -    return "$type,id=${vgaid}${memory}${max_outputs}${pciaddr}${edidoff}";
>> +    return "$type,id=${vgaid}${memory}${max_outputs}${pciaddr}${edidoff}${venus}";
>>   }
>>   
>>   sub vm_is_volid_owner {
> 



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