Re: [PATCH v4 05/16] vfio: Enforce preserved devices are retrieved via LIVEUPDATE_SESSION_RETRIEVE_FD

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Bus-specific (PCI) knowledge is hardcoded into the generic VFIO core.
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commit 15f88d928c47afcb61541ee71ab7eb8d8e0b7766
Author: David Matlack <dmatlack@google.com>

vfio: Enforce preserved devices are retrieved via LIVEUPDATE_SESSION_RETRIEVE_FD

This commit enforces that incoming VFIO devices preserved across a kexec
must be retrieved via LIVEUPDATE_SESSION_RETRIEVE_FD. Opening them via their
character device or VFIO_GROUP_GET_DEVICE_FD will fail with -EBUSY to
prevent initializing the device without the preserved state.

> diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
> index 0854f3fa1a220..5269fe021ee3a 100644
> --- a/drivers/vfio/vfio.h
> +++ b/drivers/vfio/vfio.h
> @@ -11,6 +11,7 @@
>  #include <linux/cdev.h>
>  #include <linux/module.h>
>  #include <linux/vfio.h>
> +#include <linux/pci.h>

[ ... ]

> @@ -461,4 +462,21 @@ static inline void vfio_device_debugfs_init(struct vfio_device *vdev) { }
>  static inline void vfio_device_debugfs_exit(struct vfio_device *vdev) { }
>  #endif /* CONFIG_VFIO_DEBUGFS */
>  
> +#ifdef CONFIG_PCI_LIVEUPDATE
> +static inline bool vfio_liveupdate_incoming_is_preserved(struct vfio_device *device)
> +{
> +	struct device *d = device->dev;
> +
> +	if (dev_is_pci(d))
> +		return to_pci_dev(d)->liveupdate_incoming;

Is it acceptable to hardcode bus-specific PCI knowledge into the generic
VFIO core?

The VFIO subsystem is designed to be bus-agnostic and relies on
struct vfio_device to abstract bus-specific details. By including
linux/pci.h in the generic drivers/vfio/vfio.h header and explicitly
calling dev_is_pci() and to_pci_dev(), this introduces bus-specific
logic into the core framework.

Could a generic state flag be set on the struct vfio_device object by the
bus driver (like vfio-pci) during registration or initialization instead?

> +
> +	return false;
> +}
> +#else
> +static inline bool vfio_liveupdate_incoming_is_preserved(struct vfio_device *device)
> +{
> +	return false;
> +}
> +#endif /* CONFIG_PCI_LIVEUPDATE */
> +
>  #endif

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Sashiko AI review · https://sashiko.dev/#/patchset/20260511234802.2280368-1-vipinsh@google.com?part=5