linux-kernel - Re: [PATCH v2] Documentation: Fill the gaps about entry/noinstr constraints

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Message-ID: <Ya5KM05XaUBjlthn@FVFF77S0Q05N>
Date:   Mon, 6 Dec 2021 17:36:51 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Nicolas Saenz Julienne <nsaenzju@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        rcu@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
        paulmck@...nel.org, mtosatti <mtosatti@...hat.com>,
        frederic <frederic@...nel.org>, Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH v2] Documentation: Fill the gaps about entry/noinstr
 constraints

On Fri, Dec 03, 2021 at 07:48:08PM -0800, Randy Dunlap wrote:
> On 12/1/21 12:35, Thomas Gleixner wrote:
> > +Aside of that many architectures have to save register state, e.g. debug or
> 
>                                                           state (e.g. debug) or
> 
> > +cause registers before another exception of the same type can happen. A
> 
>    ^^^^^ cannot parse (with or without the change to the previous line)

I think the difficulty here is with "cause register"? That' a register which
indicates the cause of an exception, e.g.

* MIPS has `cause` (coprocessor 0 register 13)
* arm64 / AArch64 has `ESR_ELx` (Exception Syndrome Register, ELx)

We could probably clarify this as "exception cause registers" or "exception
status registers", if that helps?

Thanks,
Mark.