linux-kernel - Re: [RFC][PATCH 3/3] x86/entry, ORC: Teach objtool/unwind

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Message-ID: <87pnbek348.fsf@nanos.tec.linutronix.de>
Date:   Fri, 08 May 2020 14:44:39 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, luto@...nel.org,
        Wei Liu <wei.liu@...nel.org>,
        Michael Kelley <mikelley@...rosoft.com>
Subject: Re: [RFC][PATCH 3/3] x86/entry, ORC: Teach objtool/unwind_orc about stack irq swizzles

Thomas Gleixner <tglx@...utronix.de> writes:
> Peter Zijlstra <peterz@...radead.org> writes:
>> Are we sure the rat-poison crap is noise for all the other system
>> vectors? I suppose it is for most since they'll do indirect calls
>> themselves anyway, right?
>
>  3) Quick
>
>     RESCHEDULE_VECTOR
>
>     POSTED_INTR_VECTOR
>     POSTED_INTR_NESTED_VECTOR
>
>         These two postit ones are weird because they are both empty and
>         just increment different irq counts.

For those 3 it's also pointless to run them on IST stack at all.

>     HYPERV_REENLIGHTENMENT_VECTOR
>
>         schedules delayed work, i,e. arms a timer which should be
>         straight forward, but does it matter?

This one shouldn't have an issue when running on task stack either, but
we can run it through the regular indirect path for now and switch it
over when it matters performance wise.

Thanks,

        tglx