On Thu, Jul 23, 2020 at 03:17:04PM +0200, Thomas Gleixner wrote:

  2) Instruction synchronization

     Trying to do instruction synchronization delayed is a clear recipe
     for hard to diagnose failures. Just because it blew not up in your
     face does not make it correct in any way. It's broken by design and
     violates _all_ rules of safe instruction patching and introduces a
     complete trainwreck in x86 NMI processing.

     If you really think that this is correct, then please have at least
     the courtesy to come up with a detailed and precise argumentation
     why this is a valid approach.

     While writing that up you surely will find out why it is not.

So delaying the sync_core() IPIs for kernel text patching _might_ be
possible, but it very much wants to be a separate patchset and not
something hidden inside a 'gem' like this.