Re: [PATCH 1/1] virtio: add driver_override support

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Mon, Dec 08, 2025 at 06:18:14PM +0200, Max Gurtovoy wrote:
> 
> On 08/12/2025 17:54, Stefan Hajnoczi wrote:
> > On Mon, Dec 08, 2025 at 04:39:25PM +0200, Max Gurtovoy wrote:
> > > Add support for the 'driver_override' attribute to Virtio devices. This
> > > allows users to control which Virtio bus driver binds to a given Virtio
> > > device.
> > > 
> > > If 'driver_override' is not set, the existing behavior is preserved and
> > > devices will continue to auto-bind to the first matching Virtio bus
> > > driver.
> > > 
> > > Signed-off-by: Avraham Evdaev <aevdaev@nvidia.com>
> > > Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
> > > ---
> > >   drivers/virtio/virtio.c | 34 ++++++++++++++++++++++++++++++++++
> > >   include/linux/virtio.h  |  4 ++++
> > >   2 files changed, 38 insertions(+)
> > What is the use case? Is there something missing in existing drivers
> > that cannot be added to them by extending the code?
> > 
> > Stefan
> 
> The main goal is to align the virtio bus with the flexibility that already exists for other buses in the Linux device model.
> On buses such as PCI and vDPA, it is possible to override or replace the default driver for a given device and bind it to an alternative driver.
> Allowing the selection of which driver is bound to a device can be useful in both development and production environments.

There are use cases for PCI and vDPA, like binding vfio_pci to a device
that would normally use its device-specific driver.

For VIRTIO, I'm not sure what the use case would be. Is there another
driver that could bind to virtio-net devices, for example?

Giving a concrete example would be useful to help people understand why
this is necessary.

Stefan

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