Re: [PATCH v2 5/5] vfio/pci: Latch all module parameters per device

[fengchengwen]

On 6/12/2026 5:35 AM, Alex Williamson wrote:
> The vfio-pci module parameters of disable_idle_d3, nointxmask, and
> disable_vga latch vfio-pci policy into vfio-pci-core globals each time
> the vfio-pci module is initialized.  The disable_idle_d3 parameter has
> already migrated to a per-device flag in order to provide consistency
> for refcounted PM operations for the lifetime of the device
> registration.
> 
> Pull the remaining vfio-pci module-parameter policy out of vfio-pci-core
> into per-device flags set at device initialization.
> 
> This also restores the mutable aspect of the disable_idle_d3 and
> nointxmask module parameters for vfio-pci, with the caveat that the
> parameters are latched into the device at probe.
> 
> A notable change for variant drivers is that their devices are no longer
> affected by vfio-pci module parameters and those drivers may need to
> adopt similar module parameters if any devices have a hidden dependency
> on vfio-pci setting non-default policy.
> 
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> ---
>  drivers/vfio/pci/vfio_pci.c      | 30 ++++++++++++++++++++++--------
>  drivers/vfio/pci/vfio_pci_core.c | 26 ++++++--------------------
>  include/linux/vfio_pci_core.h    |  4 ++--
>  3 files changed, 30 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index 0c771064c0b8..830369ff878d 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -125,9 +125,30 @@ static int vfio_pci_open_device(struct vfio_device *core_vdev)
>  	return 0;
>  }
>  
> +static int vfio_pci_init_dev(struct vfio_device *core_vdev)
> +{
> +	struct vfio_pci_core_device *vdev =
> +		container_of(core_vdev, struct vfio_pci_core_device, vdev);
> +
> +	/*
> +	 * These behaviors originated in vfio-pci and moved into
> +	 * vfio-pci-core when the driver was split; vfio-pci remains the
> +	 * only driver that toggles them.  Latch our module parameters per
> +	 * device at init time so that later parameter changes do not
> +	 * affect already-initialized devices.
> +	 */
> +	vdev->nointxmask = nointxmask;
> +	vdev->disable_idle_d3 = disable_idle_d3;
> +#ifdef CONFIG_VFIO_PCI_VGA
> +	vdev->disable_vga = disable_vga;

Since nointxmask and disable_idle_d3 already have S_IWUSR and share the same
"latch per device at init" behavior, it would be better to also add S_IWUSR
to disable_vga for permission and behavior consistency.

Runtime writes will only affect future devices, existing devices keep their
latched value, so no extra risk.

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