Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758760Ab0FRUA6 (ORCPT ); Fri, 18 Jun 2010 16:00:58 -0400 Received: from terminus.zytor.com ([198.137.202.10]:48460 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753846Ab0FRUA5 (ORCPT ); Fri, 18 Jun 2010 16:00:57 -0400 Message-ID: <4C1BD053.3050409@zytor.com> Date: Fri, 18 Jun 2010 13:00:19 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100430 Fedora/3.0.4-3.fc13 Thunderbird/3.0.4 MIME-Version: 1.0 To: Ingo Molnar CC: Andres Salomon , Andrew Morton , linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, x86@kernel.org, Mitch Bradley Subject: Re: [PATCH] x86: OLPC: add support for calling into OpenFirmware (v5) References: <20100618154245.2e00af2a@dev.queued.net> <4C1BCDD5.5040805@zytor.com> <20100618195656.GA3821@elte.hu> In-Reply-To: <20100618195656.GA3821@elte.hu> 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: 1135 Lines: 31 On 06/18/2010 12:56 PM, Ingo Molnar wrote: > > * H. Peter Anvin wrote: > >> On 06/18/2010 12:42 PM, Andres Salomon wrote: >>> + >>> + /* install OFW's PDE permanently into the kernel's pgtable */ >>> + set_pgd(&swapper_pg_dir[OLPC_OFW_PDE_NR], *ofw_pde); >>> + flush_tlb(); >>> + early_iounmap(base, sizeof(olpc_ofw_pgd) * PTRS_PER_PGD); >> >> I just realized... this flush_tlb() is actually not necessary since on x86 >> it is always legal to go from a less permissive configuration to a more >> permissive, and the initial configuration is "not present" which is >> maximally nonpermissive. >> >> Could you take it out and make sure it still works? > > small nit: an optimization barrier would still be needed if the result is > being relied on by the kernel. > In this case the optimization barrier is implicit at the return from an out of line function. -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/