From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752333AbdDRFsS (ORCPT ); Tue, 18 Apr 2017 01:48:18 -0400 Received: from ozlabs.org ([103.22.144.67]:57569 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750822AbdDRFsQ (ORCPT ); Tue, 18 Apr 2017 01:48:16 -0400 From: Michael Ellerman To: Christophe Leroy , Benjamin Herrenschmidt , Paul Mackerras , Scott Wood Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH] powerpc/mm: some cleanup of do_page_fault() In-Reply-To: <20170413145342.40ED56E667@localhost.localdomain> References: <20170413145342.40ED56E667@localhost.localdomain> User-Agent: Notmuch/0.21 (https://notmuchmail.org) Date: Tue, 18 Apr 2017 15:48:11 +1000 Message-ID: <87shl66zc4.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Christophe Leroy writes: > This patch is a bunch of small cleanups of the do_page_fault() > function: > 1/ Function store_updates_sp() checks whether the faulting > instruction is a store updating r1. Therefore we can limit its calls > to stores exceptions > 2/ Only the get_user() in store_updates_sp() has to be done outside > the mm semaphore. All the comparison can be done within the semaphore, > so only when really needed. > 3/ As we got a DSI exception, the address pointed by regs->nip is > obviously valid, otherwise we would have had a instruction exception. > So __get_user() can be used instead of get_user() > 4/ Replaced one duplicate 'trap == 0x400' by 'is_exec' > 5/ Created a 'is_user = user_mode(regs)' and replaced all > 'user_mode(regs)'. > Analysis of the assembly code shows that when using user_mode(regs), > at least the 'andi. r7,r8,16384' is redone several times, and also > the 'lwz r8,132(r31)' at times. With the new form, the 'is_user' > is mapped to cr4, then all further use of is_user results in just > things like 'beq cr4,218 ' > 6/ The 8xx has a dedicated exception for breakpoints, that directly > calls do_break() Those are probably all OK, if you send them as separate patches. > 7/ stdu and stdux only exist on PPC64, so no need to check for them > on PPC32 I don't love that, because it adds two ifdefs in the C code and the gain must be pretty small. cheers