Re: [RFC PATCH] virt: tdx-guest: Remove quote generation via ioctl

[Dan Williams <dan.j.williams@intel.com>]

Nikolay Borisov wrote:
> 
> 
> On 23.01.24 г. 19:51 ч., Kuppuswamy Sathyanarayanan wrote:
> > 
> > On 1/23/24 8:07 AM, Nikolay Borisov wrote:
> >> When this driver got merged initially there was no widely agreed upon
> >> interface how the quote generation interface will work so having an
> >> ioctl made sense. However, there's now a vendor-neutral interface via
> >> configfs. Just remove the old ioctl interface and leave only the the
> >> configfs one.
> >>
> >> Signed-off-by: Nikolay Borisov <nik.borisov@suse.com>
> >> ---
> > 
> > This ABI allows the user to get the raw report which is further used
> > for Quote generation via vsock. AFAIK, some vendors (TDX users) and
> > DCAP user libraries are still using this ABI to support attestation over
> > vsock model.
> > 
> > Don't you think we should wait till there are no users before considering
> > removing it?
> 
> Given that hw with TDX was just released I'd be surprised if there are 
> any users? But then again, this is an RFC so let's get opinions :)
> 

The assumption is that this tdx_guest_ioctl() ABI has never appeared in
an enterprise distro kernel. If that assumption is valid, it
significantly reduces the long term support exposure.

At a minimum, a build time option to disable the ioctl() path and a
runtime deprecation warning would be suitable. Certainly just removing a
never-been-enterprise-shipped ABI and see who screams is one way to
start the negotiation of the deprecation period. The current status of
no deprecation notification is difficult to justify.