From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752629AbaG1MzK (ORCPT ); Mon, 28 Jul 2014 08:55:10 -0400 Received: from smtp.citrix.com ([66.165.176.89]:45517 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751802AbaG1MzH (ORCPT ); Mon, 28 Jul 2014 08:55:07 -0400 X-IronPort-AV: E=Sophos;i="5.01,749,1400025600"; d="scan'208";a="156355935" Message-ID: <53D64828.6020209@citrix.com> Date: Mon, 28 Jul 2014 13:55:04 +0100 From: David Vrabel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Icedove/24.5.0 MIME-Version: 1.0 To: Frediano Ziglio , Konrad Rzeszutek Wilk , Boris Ostrovsky CC: xen-devel , linux-kernel Subject: Re: xen: Fix possible page fault in fifo events References: <1405432129.1749.5.camel@hamster.uk.xensource.com> In-Reply-To: <1405432129.1749.5.camel@hamster.uk.xensource.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.80.2.76] X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15/07/14 14:48, Frediano Ziglio wrote: > sync_test_bit function require a long* read access to pointer. > This is a problem if the you are using last entry in the page causing > an access to next page. If this page is not readable you get a memory > access failure (page fault). > All other x64 bit functions access memory using 32 bit operations. > For processors different than x64 long aligned operations are used. I think we should implement a set of 32-bit bit ops. We fudged around it for the arm64 problem but this second problem shows we need a better solution. David