Subject: Re: [PATCH v4 00/13] "Task_isolation" mode

From: Peter Zijlstra <[email-masked]>
Date: Thu, 23 Jul 2020 16:26:23 +0200

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.