RE: [PATCH RFC v2 0/3] Add set_dev_data and unset_dev_data support

[Tian, Kevin]

> From: Nicolin Chen <nicolinc@xxxxxxxxxx>
> Sent: Friday, April 21, 2023 3:42 PM
> 
> On Fri, Apr 21, 2023 at 07:35:52AM +0000, Tian, Kevin wrote:
> > External email: Use caution opening links or attachments
> >
> >
> > > From: Nicolin Chen <nicolinc@xxxxxxxxxx>
> > > Sent: Thursday, April 20, 2023 3:48 PM
> > >
> > > This is a pair of new uAPI/ops for user space to set an iommu specific
> > > device data for a passthrough device. This is primarily used by SMMUv3
> > > driver for now, to link the vSID and the pSID of a device that's behind
> > > the SMMU. The link (lookup table) will be used to verify any ATC_INV
> > > command from the user space for that device, and then replace the SID
> > > field (virtual SID) with the corresponding physical SID.
> > >
> > > This series is available on Github:
> > > https://github.com/nicolinc/iommufd/commits/set_dev_data-rfc-v2
> > >
> > > Thanks!
> > > Nicolin
> > >
> >
> > there is no changelog compared to v1.
> 
> Weird! How could it be missed during copy-n-paste..
> I recalled that I had it but seemingly lost it after an update.
> 
> It is in the commit message of the cover-letter though:
> https://github.com/nicolinc/iommufd/commit/5e17d270bfca2a5e3e7401d4b
> f58ae53eb7a8a55
> --------------------------------------------------------
> Changelog
> v2:
>  * Integrated the uAPI into VFIO_DEVICE_BIND_IOMMUFD call
>  * Renamed the previous set_rid_user to set_dev_data, to decouple from
>    the PCI regime.
> v1:
>  https://lore.kernel.org/all/cover.1680762112.git.nicolinc@xxxxxxxxxx/
> --------------------------------------------------------
> 
> > Could you add some words why changing from passing the information
> > in an iommufd ioctl to bind_iommufd? My gut-feeling leans toward
> > the latter option...
> 
> Yea. Jason told me to decouple it from PCI. And merge it into
> a general uAPI. So I picked the BIND ioctl.
> 

'decouple it from PCI' is kind of covered by renaming set_rid
to set_data. but I didn't get why this has to be merged with another
uAPI. Once iommufd_device is created we could have separate
ioctls to poke its attributes individually. What'd be broken if this
is not done at BIND time?