Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754550Ab2JFS4V (ORCPT ); Sat, 6 Oct 2012 14:56:21 -0400 Received: from mga02.intel.com ([134.134.136.20]:2962 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751699Ab2JFS4U (ORCPT ); Sat, 6 Oct 2012 14:56:20 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.80,545,1344236400"; d="scan'208";a="202476995" Message-ID: <50707ECD.2070300@zytor.com> Date: Sat, 06 Oct 2012 11:56:13 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0 MIME-Version: 1.0 To: Andi Kleen CC: Alexander Duyck , konrad.wilk@oracle.com, tglx@linutronix.de, mingo@redhat.com, rob@landley.net, akpm@linux-foundation.org, joerg.roedel@amd.com, bhelgaas@google.com, shuahkhan@gmail.com, linux-kernel@vger.kernel.org, devel@linuxdriverproject.org, x86@kernel.org, torvalds@linux-foundation.org Subject: Re: [RFC PATCH 0/7] Improve swiotlb performance by using physical addresses References: <20121004002113.5016.66913.stgit@gitlad.jf.intel.com> <506F3670.4020202@intel.com> <20121005200245.GQ16230@one.firstfloor.org> <506F6BF2.8030500@intel.com> <20121006175751.GS16230@one.firstfloor.org> In-Reply-To: <20121006175751.GS16230@one.firstfloor.org> X-Enigmail-Version: 1.4.3 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1068 Lines: 29 On 10/06/2012 10:57 AM, Andi Kleen wrote: > > Maybe it's just me, but that's somehow sad for one if() and a su > btraction > > BTW __pa used to be a simple subtraction, the if () was just added to > handle the few call sites for x86-64 that do __pa(&text_symbol). > Maybe we should just go back to the old __pa_symbol() for those cases, > then __pa could be the simple subtraction it used to was again > and it could be inlined and everyone would be happy. > I wonder how much the double-mapping actually buys us, if we could get a PIE-type memory model that doesn't try to create GOT references. We would unambiguously lose out the cases where we currently can do symbol(index) but I wonder how much the impact actually is. The advantage would be that it would give us way more room to do kernel space ASR. -hpa -- 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/