From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1758390AbdKGRYc (ORCPT <rfc822;w@1wt.eu>);
        Tue, 7 Nov 2017 12:24:32 -0500
Received: from mga07.intel.com ([134.134.136.100]:20140 "EHLO mga07.intel.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1752181AbdKGRYb (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 7 Nov 2017 12:24:31 -0500
X-ExtLoop1: 1
X-IronPort-AV: E=Sophos;i="5.44,359,1505804400"; 
   d="scan'208";a="918600287"
Date: Tue, 7 Nov 2017 09:24:29 -0800
From: Andi Kleen <ak@linux.intel.com>
To: Milind Chabbi <chabbi.milind@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Jiri Olsa <jolsa@redhat.com>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Hari Bathini <hbathini@linux.vnet.ibm.com>,
        Jin Yao <yao.jin@linux.intel.com>, Kan Liang <kan.liang@intel.com>,
        Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] perf/core: fast breakpoint modification via
 _IOC_MODIFY_BREAKPOINT.
Message-ID: <20171107172429.GG5320@tassilo.jf.intel.com>
References: <1510006156-18988-1-git-send-email-chabbi.milind@gmail.com>
 <20171107081457.GE3326@worktop>
 <CAMmz+Yks+gqSwvSd6i-_somNy7+Gsqdz7xfAjpqZ3Enha31dJQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAMmz+Yks+gqSwvSd6i-_somNy7+Gsqdz7xfAjpqZ3Enha31dJQ@mail.gmail.com>
User-Agent: Mutt/1.9.1 (2017-09-22)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, Nov 07, 2017 at 07:43:35AM -0800, Milind Chabbi wrote:
> Peter,
> 
> Generic update perf_event_attr interface is noble but impractical.
> It will cause a validation nightmare.
> Many of the behaviors or choices will become hard to reason.

I don't think you would necessarily need to support modifying
all of this. Just define a general interface that could be used
to modify these things, but right now it would be only
implemented for the special case of breakpoints.

Your ioctl is very near it anyways, just need to change
the name and do more sanity checking on the input values.

-Andi