[PATCH v2 5/9] vfio/mdev: Consolidate all the device_api sysfs into the core code

[Jason Gunthorpe]

On Fri, Sep 10, 2021 at 01:10:46PM +0100, Christoph Hellwig wrote:
> On Thu, Sep 09, 2021 at 04:38:45PM -0300, Jason Gunthorpe wrote:
> > Every driver just emits a static string, simply feed it through the ops
> > and provide a standard sysfs show function.
> 
> Looks sensible.  But can you make the attribute optional and add a
> comment marking it deprecated?  Because it really is completely useless.
> We don't version userspace APIs, userspae has to discover new features
> individually by e.g. finding new sysfs files or just trying new ioctls.

To be honest I have no idea what side effects that would have..

device code search tells me libvirt reads it and stuffs it into some
XML

Something called mdevctl touches it, feeds it into some JSON and
other stuff..

qemu has some VFIO_DEVICE_API_* constants but it is all dead code

I agree it shouldn't have been there in the first place

Cornelia? Alex? Any thoughts?

Jason