linux-kernel - Re: [patch part-II V2 11/13] x86/speculation/mds: Mark mds_user_clear_cpu_buffers() __always

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Date:   Tue, 10 Mar 2020 17:38:01 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Alexandre Chartre <alexandre.chartre@...cle.com>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Steven Rostedt <rostedt@...dmis.org>,
        Brian Gerst <brgerst@...il.com>,
        Juergen Gross <jgross@...e.com>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [patch part-II V2 11/13] x86/speculation/mds: Mark mds_user_clear_cpu_buffers() __always_inline

Alexandre Chartre <alexandre.chartre@...cle.com> writes:
> On 3/8/20 11:24 PM, Thomas Gleixner wrote:
>> -static inline void mds_user_clear_cpu_buffers(void)
>> +static __always_inline void mds_user_clear_cpu_buffers(void)
>>   {
>>   	if (static_branch_likely(&mds_user_clear))
>>   		mds_clear_cpu_buffers();
>> 
>
> Reviewed-by: Alexandre Chartre <alexandre.chartre@...cle.com>
>
> I am just wondering if it would be worth defining a new function attribute to
> identify functions which shouldn't be trace/probe more clearly. For example:
>
> #define no_trace_and_probe __always_inline
>
> static no_trace_and_probe void mds_user_clear_cpu_buffers(void)
> {
>          ...
> }
>
> I am just concerned that overtime we might forgot that a function is defined
> __always_inline just because it shouldn't be traced/probed.

True, for exactly that reason we are reconsidering the whole annotation
business by putting stuff into a separate section so we get tools
support for finding things which escape. See the discussion at:

  https://lore.kernel.org/lkml/87mu8p797b.fsf@nanos.tec.linutronix.de/

Peter and I are working on this right now, so you might end up reviewing
this pile in different form yet another time :(

Thanks,

        tglx