[pve-devel] superseded: [RFC PATCH qemu-server] pci: add 'keep-driver' option

[Dominik Csapak]

superseded by: 
https://lore.proxmox.com/pve-devel/20251023130641.4190006-1-d.csapak@proxmox.com/T/#u

On 8/12/25 11:59 AM, Dominik Csapak wrote:
> by default, pci devices will be bound to 'vfio-pci' driver and reset.
> For most devices this is necessary, but there are a few exceptions,
> e.g.:
> 
> * some mellanox nics have support for the driver 'mlx5_vfio_pci'
> * intel flex gpus have support for 'i915_vfio_pci'
> * (maybe some more i don't know about)
> 
> both of these drivers play the role of the vfio-pci drivers themselves,
> so no rebinding or resetting necessary. Those drivers usually have more
> functionality than the default vfio driver, like support for
> live-migration.
> 
> To be able to configure that on our side, introduce the 'keep-driver'
> option for 'hostpciX', which will not rebind/reset the device.
> 
> Signed-off-by: Dominik Csapak <d.csapak at proxmox.com>
> ---
> sending as RFC, since i'm not sure if we want to go this (generic)
> approach, or if we e.g. want to make special configs/cases for driver we
> know. Pro of this approach is that we don't have to add more drivers in
> the future, but con is that it has some potential to confuse users when
> it does not work the way they though it would.
> 
>   src/PVE/QemuServer/PCI.pm | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/src/PVE/QemuServer/PCI.pm b/src/PVE/QemuServer/PCI.pm
> index e7a9a610..84a56998 100644
> --- a/src/PVE/QemuServer/PCI.pm
> +++ b/src/PVE/QemuServer/PCI.pm
> @@ -124,6 +124,13 @@ EODESCR
>           optional => 1,
>           description => "Override PCI subsystem device ID visible to guest",
>       },
> +    'keep-driver' => {
> +        type => 'boolean',
> +        optional => 1,
> +        default => 0,
> +        description => "If this is set, does not bind the device to vfio-pci and does not reset"
> +            . "the device. Useful for VF that already have the correct driver loaded.",
> +    },
>   };
>   PVE::JSONSchema::register_format('pve-qm-hostpci', $hostpci_fmt);
>   
> @@ -736,7 +743,7 @@ sub prepare_pci_device {
>           if !PVE::SysFSTools::check_iommu_support();
>       die "no pci device info for device '$pciid'\n" if !$info;
>   
> -    if ($device->{nvidia}) {
> +    if ($device->{nvidia} || $device->{'keep-driver'}) {
>           # nothing to do
>       } elsif (my $mdev = $device->{mdev}) {
>           my $uuid = generate_mdev_uuid($vmid, $index);