Re: [pve-devel] [PATCH qemu-server 1/1] automatically add 'uuid' parameter when passing through NVIDIA vGPU

[Wolfgang Bumiller <w.bumiller@proxmox.com>]

On Tue, Jul 26, 2022 at 08:55:58AM +0200, Dominik Csapak wrote:
> When passing through an NVIDIA vGPU via mediated devices, their
> software needs the qemu process to have the 'uuid' parameter set to the
> one of the vGPU. Since it's currently not possible to pass through multiple
> vGPUs to one VM (seems to be an NVIDIA driver limitation at the moment),
> we don't have to take care about that.
> 
> Sadly, the place we do this, it does not show up in 'qm showcmd' as we
> don't (want to) query the pci devices in that case, and then we don't
> have a way of knowing if it's an NVIDIA card or not. But since this
> is informational with QEMU anyway, i'd say we can ignore that.
> 
> Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
> ---
>  PVE/QemuServer.pm     | 8 +++++++-
>  PVE/QemuServer/PCI.pm | 4 +++-
>  2 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
> index 7d9cf22..c4eb031 100644
> --- a/PVE/QemuServer.pm
> +++ b/PVE/QemuServer.pm
> @@ -5597,7 +5597,13 @@ sub vm_start_nolock {
>  	for my $id (sort keys %$pci_devices) {
>  	    my $d = $pci_devices->{$id};
>  	    for my $dev ($d->{pciid}->@*) {
> -		PVE::QemuServer::PCI::prepare_pci_device($vmid, $dev->{id}, $id, $d->{mdev});
> +		my $info = PVE::QemuServer::PCI::prepare_pci_device($vmid, $dev->{id}, $id, $d->{mdev});
> +
> +		# nvidia grid needs the uuid of the mdev as qemu parameter
> +		if ($d->{mdev} && $info->{vendor} eq '10de') {
> +		    my $uuid = PVE::QemuServer::PCI::generate_mdev_uuid($vmid, $id);
> +		    push @$cmd, '-uuid', $uuid;

You mention you can only pass through one device, but I'd still prefer
the code to make sure we only pass a single `-uuid` parameter here,
since this is not at all clear when just reading the code.

Otherwise this seems fine.

> +		}
>  	    }
>  	}
>      };
> diff --git a/PVE/QemuServer/PCI.pm b/PVE/QemuServer/PCI.pm
> index 23fe508..3d0e70e 100644
> --- a/PVE/QemuServer/PCI.pm
> +++ b/PVE/QemuServer/PCI.pm
> @@ -253,7 +253,7 @@ sub get_pci_addr_map {
>      return $pci_addr_map;
>  }
>  
> -my sub generate_mdev_uuid {
> +sub generate_mdev_uuid {
>      my ($vmid, $index) = @_;
>      return sprintf("%08d-0000-0000-0000-%012d", $index, $vmid);
>  }
> @@ -514,6 +514,8 @@ sub prepare_pci_device {
>  	die "can't reset PCI device '$pciid'\n"
>  	    if $info->{has_fl_reset} && !PVE::SysFSTools::pci_dev_reset($info);
>      }
> +
> +    return $info;
>  }
>  
>  my $RUNDIR = '/run/qemu-server';
> -- 
> 2.30.2