linux-kernel - Re: [PATCH v3 1/2] Documentation: Fill the gaps about entry/noinstr constraints

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Message-ID: <87a6gzcepi.ffs@tglx>
Date:   Fri, 17 Dec 2021 18:40:25 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Nicolas Saenz Julienne <nsaenzju@...hat.com>, mark.rutland@....com,
        paulmck@...nel.org
Cc:     rostedt@...dmis.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, rcu@...r.kernel.org,
        peterz@...radead.org, mtosatti@...hat.com, frederic@...nel.org,
        corbet@....net, Nicolas Saenz Julienne <nsaenzju@...hat.com>
Subject: Re: [PATCH v3 1/2] Documentation: Fill the gaps about entry/noinstr
 constraints

Nicolas,

On Fri, Dec 17 2021 at 11:57, Nicolas Saenz Julienne wrote:
> +Non-instrumentable code - noinstr
> +---------------------------------
> +
> +Most instrumentation facilities depend on RCU, so intrumentation is prohibited
> +for entry code before RCU starts watching and exit code after RCU stops
> +watching. In addition, many architectures must save and restore register state,
> +which means that (for example) a breakpoint in the breakpoint entry code would
> +overwrite the debug registers of the initial breakpoint.
> +
> +Such code must be marked with the 'noinstr' attribute, placing that code into a
> +special section inaccessible to instrumentation and debug facilities. Some
> +functions are partially instrumentable, which is handled by marking them nointr

s/nointr/noinstr/

Thanks for polishing this!

       tglx