Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
In-Reply-To: <20180412192800.15708-13-mathieu.desnoyers@efficios.com>
References: <20180412192800.15708-1-mathieu.desnoyers@efficios.com> <20180412192800.15708-13-mathieu.desnoyers@efficios.com>
From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 12 Apr 2018 12:43:27 -0700
Message-ID: <CA+55aFxcJ2V_1BoW0Cct=Kkp7REkgiU_BTimGdmoFmWHaWaZ-g@mail.gmail.com>
Subject: Re: [RFC PATCH for 4.18 12/23] cpu_opv: Provide cpu_opv system call (v7)
To:     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Dave Watson <davejwatson@fb.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>,
        Paul Turner <pjt@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Russell King <linux@arm.linux.org.uk>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "H . Peter Anvin" <hpa@zytor.com>, Andrew Hunter <ahh@google.com>,
        Andi Kleen <andi@firstfloor.org>, Chris Lameter <cl@linux.com>,
        Ben Maurer <bmaurer@fb.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Josh Triplett <josh@joshtriplett.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Michael Kerrisk <mtk.manpages@gmail.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Apr 12, 2018 at 12:27 PM, Mathieu Desnoyers
<mathieu.desnoyers@efficios.com> wrote:
> The cpu_opv system call executes a vector of operations on behalf of
> user-space on a specific CPU with preemption disabled. It is inspired
> by readv() and writev() system calls which take a "struct iovec"
> array as argument.

Do we really want the page pinning?

This whole cpu_opv thing is the most questionable part of the series,
and the page pinning is the most questionable part of cpu_opv for me.

Can we plan on merging just the plain rseq parts *without* this all
first, and then see the cpu_opv thing as a "maybe future expansion"
part.

I think that would make Andy happier too.

             Linus