Re: [PATCH V4 10/13] PCI / VFIO: Add 'override_only' support for VFIO PCI sub system

[Alex Williamson <alex.williamson@redhat.com>]

On Wed, 25 Aug 2021 16:51:36 +0300
Yishai Hadas <yishaih@nvidia.com> wrote:
> diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
> index 7c97fa8e36bc..c3edbf73157e 100644
> --- a/scripts/mod/file2alias.c
> +++ b/scripts/mod/file2alias.c
> @@ -426,7 +426,7 @@ static int do_ieee1394_entry(const char *filename,
>  	return 1;
>  }
>  
> -/* Looks like: pci:vNdNsvNsdNbcNscNiN. */
> +/* Looks like: pci:vNdNsvNsdNbcNscNiN or <prefix>_pci:vNdNsvNsdNbcNscNiN. */
>  static int do_pci_entry(const char *filename,
>  			void *symval, char *alias)
>  {
> @@ -440,8 +440,12 @@ static int do_pci_entry(const char *filename,
>  	DEF_FIELD(symval, pci_device_id, subdevice);
>  	DEF_FIELD(symval, pci_device_id, class);
>  	DEF_FIELD(symval, pci_device_id, class_mask);
> +	DEF_FIELD(symval, pci_device_id, override_only);
>  
> -	strcpy(alias, "pci:");
> +	if (override_only & PCI_ID_F_VFIO_DRIVER_OVERRIDE)
> +		strcpy(alias, "vfio_pci:");
> +	else
> +		strcpy(alias, "pci:");

I'm a little concerned that we're allowing unknown, non-zero
override_only values to fall through to create "pci:" alias matches.
Should this be something like:

	if (override_only & PCI_ID_F_VFIO_DRIVER_OVERRIDE) {
		strcpy(alias, "vfio_pci:");
	} else if (override_only) {
		warn("Unknown PCI driver_override alias %08X\n",
			driver_override);
		return 0;
	} else {
		strcpy(alias, "pci:");
	}

And then if we can only have a single bit set in override_only (I
can't think of a use case for a single entry to have multiple
override options), should PCI_DEVICE_DRIVER_OVERRIDE() be defined to
take a "driver_override_shift" value where .driver_override is assigned
(1 << driver_override_shift)?  That would encode the semantics in the
prototypes a little better.  Thanks,

Alex

>  	ADD(alias, "v", vendor != PCI_ANY_ID, vendor);
>  	ADD(alias, "d", device != PCI_ANY_ID, device);
>  	ADD(alias, "sv", subvendor != PCI_ANY_ID, subvendor);