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Date:   Thu, 23 Jul 2020 16:26:23 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Alex Belits <abelits@...vell.com>,
        "frederic@...nel.org" <frederic@...nel.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        Prasun Kapoor <pkapoor@...vell.com>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will@...nel.org" <will@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH v4 00/13] "Task_isolation" mode

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.

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