Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932616AbWLMIi3 (ORCPT ); Wed, 13 Dec 2006 03:38:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932619AbWLMIi3 (ORCPT ); Wed, 13 Dec 2006 03:38:29 -0500 Received: from ug-out-1314.google.com ([66.249.92.174]:37757 "EHLO ug-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932616AbWLMIi2 (ORCPT ); Wed, 13 Dec 2006 03:38:28 -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=Xhh12mTqeF4IYWuqC2dqMEQcrJjgbTWYfH4M7Z1GJOe8gzPlBVMSZFtUDWD3eZax3HL6bF5k+WvgxIEHQom7ecPQW+Ycb1qdusRkvDxmmJZqEwaJSU75eF+ayxRN/0LFlw4v1mL20Eryy/sUms/diYKiBMGBUpEBScMFnJgOy5E= Message-ID: Date: Wed, 13 Dec 2006 09:38:26 +0100 From: "Franck Bui-Huu" To: "Jaya Kumar" Subject: Re: [RFC 2.6.19 1/1] fbdev,mm: hecuba/E-Ink fbdev driver v2 Cc: linux-fbdev-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, linux-mm@kvack.org In-Reply-To: <45a44e480612111554j1450f35ub4d9932e5cd32d4@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <200612111046.kBBAkV8Y029087@localhost.localdomain> <457D895D.4010500@innova-card.com> <45a44e480612111554j1450f35ub4d9932e5cd32d4@mail.gmail.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 989 Lines: 22 On 12/12/06, Jaya Kumar wrote: > I think that PTEs set up by vmalloc are marked cacheable and via the > above nopage end up as cacheable. I'm not doing DMA. So the accesses > are through the cache so I don't think cache aliasing is an issue for > this case. Please let me know if I misunderstood. > This issue is not related to DMA: there are 2 different virtual addresses that can map the same physical address. If these 2 virtual addresses use 2 different data cache entries then you have a cache aliasing issue. In your case the 2 different virtual addresses are (1) the one got by the kernel (returned by vmalloc) (2) the one got by the application (returned by mmap). Hope that helps. -- Franck - 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/