Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758892AbWLFA5P (ORCPT ); Tue, 5 Dec 2006 19:57:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758915AbWLFA5P (ORCPT ); Tue, 5 Dec 2006 19:57:15 -0500 Received: from nz-out-0506.google.com ([64.233.162.238]:33187 "EHLO nz-out-0102.google.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1758892AbWLFA5O (ORCPT ); Tue, 5 Dec 2006 19:57:14 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=ATaLLLDkfzY//gtMw6u4pNrT/DgIFDfWKvnAxU7X3atX0LS9TGo4RI6UVTt7XHKnxQqaLBQQM32uvc5AYLlVZMlpb5eVVhpew3ktlpZWwc/wegM93XEWYVAdHdxzS4NNRZ07kGKNr12o4cjxm47vLhPjFw1oJAHx36nZT3YsJlg= Message-ID: Date: Tue, 5 Dec 2006 16:57:12 -0800 From: "Matt Reimer" To: "David Miller" Subject: Re: [PATCH] mm: D-cache aliasing issue in cow_user_page Cc: linux-kernel@vger.kernel.org In-Reply-To: <20061205.132412.116353924.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20061205.132412.116353924.davem@davemloft.net> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1089 Lines: 26 On 12/5/06, David Miller wrote: > From: "Matt Reimer" > Date: Mon, 4 Dec 2006 23:38:13 -0800 > > > In light of James Bottomsley's commit[1] declaring that kmap() and > > friends now have to take care of coherency issues, is the patch "mm: > > D-cache aliasing issue in cow_user_page"[2] correct, or could it > > potentially cause a slowdown by calling flush_dcache_page() a second > > time (i.e. once in an architecture-specific kmap() implementation, and > > once in cow_user_page())? > > kmap() is a NOP unless HIGHMEM is configured. > > Therefore, it cannot possibly take care of D-cache aliasing issues > across the board. Right, but isn't he declaring that each architecture needs to take care of this? So, say, on ARM we'd need to make kunmap() not a NOP and call flush_dcache_page() ? Matt - 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/