Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754251AbZITJfR (ORCPT ); Sun, 20 Sep 2009 05:35:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754167AbZITJfR (ORCPT ); Sun, 20 Sep 2009 05:35:17 -0400 Received: from mail-yx0-f199.google.com ([209.85.210.199]:61653 "EHLO mail-yx0-f199.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753153AbZITJfQ convert rfc822-to-8bit (ORCPT ); Sun, 20 Sep 2009 05:35:16 -0400 MIME-Version: 1.0 In-Reply-To: <20090920081550.GA830@n2100.arm.linux.org.uk> References: <20090919110316.GA23452@n2100.arm.linux.org.uk> <20090920081550.GA830@n2100.arm.linux.org.uk> Date: Sun, 20 Sep 2009 12:35:19 +0300 Message-ID: Subject: Re: [PATCH 1/2] ARM: Pass IFSR register to do_PrefetchAbort() From: "Kirill A. Shutemov" To: Russell King - ARM Linux Cc: Bityutskiy Artem , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Koskinen Aaro Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1733 Lines: 41 On Sun, Sep 20, 2009 at 11:15 AM, Russell King - ARM Linux wrote: > On Sat, Sep 19, 2009 at 12:03:16PM +0100, Russell King - ARM Linux wrote: >> On Fri, Sep 18, 2009 at 11:55:42PM +0300, Kirill A. Shutemov wrote: >> > It needed for proper prefetch abort handling on ARMv7. >> >> I think the only thing which is missing is an explaination about why >> this is desirable given that only later CPUs can give this additional >> information. > > So you've posted it to the patch system, without further discussion here. > > I think the solution is wrong - it makes instruction permission faults > unnecessarily noisy, which is not what the decoding table is supposed > to be doing.  The decoding table's bad entries are there to catch those > _unexpected_ cases. > > Instead, I suggest that you have a look at this: > >        if (fsr & (1 << 11)) /* write? */ >                mask = VM_WRITE; >        else >                mask = VM_READ|VM_EXEC|VM_WRITE; > >        fault = VM_FAULT_BADACCESS; >        if (!(vma->vm_flags & mask)) >                goto out; > > in __do_page_fault - if we are handling a prefetch abort, we really only > want to check that the VMA has VM_EXEC permission, not that it can be > read and written as well. > Ok, so __do_page_fault() should know where we are: in data abort or in prefetch abort. What is right way to do it? Should we create one more argument or use one of reserved bits IFSR? -- 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/