linux-kernel - Re: [RFC PATCH] rseq: x86: implement abort-at-ip extension

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Message-ID: <87sftt6j0u.fsf@mid.deneb.enyo.de>
Date:   Wed, 12 Jan 2022 17:00:49 +0100
From:   Florian Weimer <fw@...eb.enyo.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        paulmck <paulmck@...nel.org>, Boqun Feng <boqun.feng@...il.com>,
        "H. Peter Anvin" <hpa@...or.com>, Paul Turner <pjt@...gle.com>,
        linux-api <linux-api@...r.kernel.org>,
        Christian Brauner <christian.brauner@...ntu.com>,
        carlos <carlos@...hat.com>
Subject: Re: [RFC PATCH] rseq: x86: implement abort-at-ip extension

* Peter Zijlstra:

> On Wed, Jan 12, 2022 at 04:16:36PM +0100, Florian Weimer wrote:
>
>> You could perhaps push a signal frame onto the stack.  It's going to
>> be expensive, but it's already in the context switch path, so maybe it
>> does not matter.
>
> Please no! Signals are a trainwreck that need change (see the whole
> AVX-512 / AMX saga), we shouldn't use more of that just cause.

If it's a signal, it should be modeled as such.  I think it's pretty
close to a synchronous signal.