From mboxrd@z Thu Jan  1 00:00:00 1970
From: josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org
Subject: Re: [RFC PATCH] getcpu_cache system call: caching current CPU
 number (x86)
Date: Mon, 20 Jul 2015 13:07:53 -0700
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To: Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>
Cc: Florian Weimer <fweimer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Ben Maurer <bmaurer-b10kYP2dOMg@public.gmane.org>, Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, libc-alpha <libc-alpha-9JcytcrH/bA+uJoB2kUjGw@public.gmane.org>, linux-api <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, =?utf-8?B?T25kxZllaiBCw61sa2E=?= <neleai-9Vj9tDbzfuSlVyrhU4qvOw@public.gmane.org>, rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>, Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Mathieu Desnoyers <mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>, "Paul E. McKenney" <paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>, Lai Jiangshan <laijs-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>, Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Andrew Hunter <ahh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
List-Id: linux-api@vger.kernel.org

On Mon, Jul 20, 2015 at 10:41:09AM -0700, Andy Lutomirski wrote:
> On Mon, Jul 20, 2015 at 8:32 AM, Florian Weimer <fweimer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> > On 07/20/2015 05:31 PM, Andy Lutomirski wrote:
> >> On Jul 20, 2015 1:35 AM, "Florian Weimer" <fweimer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> >>>
> >>> On 07/18/2015 01:33 AM, Andy Lutomirski wrote:
> >>>
> >>>> I think the API should be "set gsbase to x + y*(cpu number)".  On
> >>>> x86_64, userspace just allocates a big swath of virtual space and
> >>>> populates it as needed.
> >>>
> >>> This will break WINE and similar applications which use %gs today.
> >>
> >> Presumably WINE could just opt not to use this facility, just like
> >> WINE will have to opt out of whatever the enterprise people who want
> >> WRGSBASE were thinking of doing with it.
> >
> > How is this possible if it's process-global attribute and glibc or some
> > library in the process starts using it?
> >
> 
> glibc will have to expose a way to turn it off, I guess. (ELF flag?)

Or a way to turn it on.

- Josh Triplett