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

[Dominik Csapak]

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);
-- 
2.39.5