Re: [PATCH qemu-server v4 6/7] pci: call hookscript for each prepared pci device

["Elias Huhsovitz" <e.huhsovitz@proxmox.com>]

One comment inline.

On Tue Aug 25, 2026 at 3:54 PM CEST, Dominik Csapak wrote:
> There are situations where a user might want to do extra things
> for a passed through PCI device after it has been prepared/created (e.g.
> in case of vGPU/mdev) but before the actual QEMU process is started.
>
> Two examples are (both are used with NVIDIA vGPUs):
> * setting 'vgpu_params' such as removing the frame-rate-limiter
> * setting the gpu_instance_id for MIG devices
>
> So instead of creating (nvidia-specific) interfaces for these, give a
> user the ability to do it themselves via the hookscript as a first step.
>
> Call it for each prepared device, so that we can give the hookscript the
> 'hostpciX' id, and the used uuid (in case of mdevs) or the pci id (in
> case of regular or modern vGPU passthrough).
>
> A failing hookscript aborts, and blocks the VM start.
>
> Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
> ---
>  src/PVE/QemuServer/PCI.pm | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/src/PVE/QemuServer/PCI.pm b/src/PVE/QemuServer/PCI.pm
> index 5d2fdabb..755945a9 100644
> --- a/src/PVE/QemuServer/PCI.pm
> +++ b/src/PVE/QemuServer/PCI.pm
> @@ -5,6 +5,7 @@ use strict;
>  
>  use IO::File;
>  
> +use PVE::GuestHelpers;
>  use PVE::JSONSchema;
>  use PVE::Mapping::PCI;
>  use PVE::SysFSTools;
> @@ -728,10 +729,17 @@ sub prepare_pci_devices {
>              if ($d->{mdev} || $d->{nvidia}) {
>                  warn $@ if $@;
>                  $chosen_mdev = $info;
> -                last if $chosen_mdev; # if successful, we're done
>              } else {
>                  die $@ if $@;
>              }
> +
> +            next if !defined($info);
> +
> +            my $params = { id => $id, pciid => $info->{name} };
> +            $params->{mdev_uuid} = $info->{uuid} if defined($info->{uuid});
> +            PVE::GuestHelpers::exec_hookscript($conf, $vmid, 'post-pci-prepare', 1, $params);

Passing $stop_on_error=1 might causes existing hookscripts do 'die'.

The current example hookscript found under
/usr/share/pve-docs/examples/guest-example-hookscript.pl
recommends a pattern of dying, if an unknown hookscript-phase is used.

I would assume that most users are currently using such a pattern.

We now call exec_hookscript with `$stop_on_error=1`. Users that have an
active hookscript and an active PCI device will experience the following
error on VM startup:

GUEST HOOK: 202 post-pci-prepare
got unknown phase 'post-pci-prepare'
TASK ERROR: hookscript error for 202 on post-pci-prepare:
command '/var/lib/vz/snippets/guest-example-hookscript-old.pl 202 post-pci-prepare' failed:
exit code 255

See my review for patch 7/7 for my suggestions of handling this.

> +
> +            last if defined($chosen_mdev);
>          }
>  
>          next if !$d->{mdev} && !$d->{nvidia};