Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752907AbbBYKu0 (ORCPT ); Wed, 25 Feb 2015 05:50:26 -0500 Received: from mail-wg0-f45.google.com ([74.125.82.45]:41848 "EHLO mail-wg0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751641AbbBYKuY (ORCPT ); Wed, 25 Feb 2015 05:50:24 -0500 Date: Wed, 25 Feb 2015 11:50:20 +0100 From: Ingo Molnar To: Borislav Petkov Cc: Andy Lutomirski , Denys Vlasenko , Oleg Nesterov , Rik van Riel , X86 ML , Linux Kernel Mailing List Subject: Re: [RFC PATCH] x86, fpu: Use eagerfpu by default on all CPUs Message-ID: <20150225105020.GF554@gmail.com> References: <20150225103701.GA3226@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150225103701.GA3226@pd.tnic> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 839 Lines: 25 * Borislav Petkov wrote: > On Tue, Feb 24, 2015 at 04:07:07PM -0800, Andy Lutomirski wrote: > > > I'd prefer a different partial solution: encourage > > everyone to clear the xstate before making syscalls > > (using e.g. vzeroall). In fact, maybe user code should > > aggressively clear newly-unused xstate. > > We don't trust userspace. We certainly don't, but in this case it's a performance optimization detail: if user-space clears unused xstate in a way that the CPU recognizes it (for example VZEROALL) then it might get faster context switches. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/