From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <andi-Vw/NltI1exuRpAAqCnN02g@public.gmane.org>
Subject: Re: [RFC PATCH v3 for 4.15 08/24] Provide cpu_opv system call
Date: Mon, 20 Nov 2017 10:49:27 -0800
Message-ID: <20171120184927.GK2482@two.firstfloor.org>
References: <20171114200414.2188-1-mathieu.desnoyers@efficios.com>
 <20171114200414.2188-9-mathieu.desnoyers@efficios.com>
 <alpine.DEB.2.20.1711162215100.2109@nanos>
 <1766414702.18278.1511194398489.JavaMail.zimbra@efficios.com>
 <alpine.DEB.2.20.1711201831490.1734@nanos>
 <204285712.18480.1511203151076.JavaMail.zimbra@efficios.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Return-path: <linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Content-Disposition: inline
In-Reply-To: <204285712.18480.1511203151076.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
To: Mathieu Desnoyers <mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
Cc: Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>, Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, "Paul E. McKenney" <paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>, Boqun Feng <boqun.feng-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>, Dave Watson <davejwatson-b10kYP2dOMg@public.gmane.org>, linux-kernel <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, linux-api <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>, Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>, Andrew Hunter <ahh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Andi Kleen <andi-Vw/NltI1exuRpAAqCnN02g@public.gmane.org>, Chris Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>, Ben Maurer <bmaurer-b10kYP2dOMg@public.gmane.org>, rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>, Josh Triplett <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org>, Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Catalin Marinas <cata>
List-Id: linux-api@vger.kernel.org

> Having cpu_opv do a 4k memcpy allow it to handle scenarios where
> rseq fails to progress.

If anybody ever gets that right. It will be really hard to just
test such a path.

It also seems fairly theoretical to me. Do you even have a 
test case where the normal path stops making forward progress?

-Andi