Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030261AbcLWBBJ (ORCPT ); Thu, 22 Dec 2016 20:01:09 -0500 Received: from us01smtprelay-2.synopsys.com ([198.182.47.9]:44638 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756712AbcLWBBI (ORCPT ); Thu, 22 Dec 2016 20:01:08 -0500 Subject: Re: [PATCH] arc: enable unaligned access in kernel mode To: Alexey Brodkin , References: <1482320454-5731-1-git-send-email-abrodkin@synopsys.com> CC: , John Crispin Newsgroups: gmane.linux.kernel,gmane.linux.kernel.arc From: Vineet Gupta Message-ID: <3d30577c-3994-a1b4-385f-38094f7f7f36@synopsys.com> Date: Thu, 22 Dec 2016 17:00:59 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: <1482320454-5731-1-git-send-email-abrodkin@synopsys.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.10.161.52] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2030 Lines: 52 On 12/21/2016 03:40 AM, Alexey Brodkin wrote: > This enables misaligned access handling even in kernel mode. > Some wireless drivers (ath9k-htc and mt7601u) use misaligned accesses > here and there and to cope with that without fixing stuff in the drivers > we're just gracefully handling it on ARC. > > Signed-off-by: Alexey Brodkin > Cc: John Crispin > --- > arch/arc/kernel/unaligned.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arc/kernel/unaligned.c b/arch/arc/kernel/unaligned.c > index abd961f3e763..58b7415e47ca 100644 > --- a/arch/arc/kernel/unaligned.c > +++ b/arch/arc/kernel/unaligned.c > @@ -205,8 +205,8 @@ int misaligned_fixup(unsigned long address, struct pt_regs *regs, > struct disasm_state state; > char buf[TASK_COMM_LEN]; > > - /* handle user mode only and only if enabled by sysadmin */ > - if (!user_mode(regs) || !unaligned_enabled) > + /* handle only if enabled by sysadmin */ > + if (!unaligned_enabled) This in theory seems OK but AFAIKR we discussed this internally for STAR 9000974739- [openwrt/AXS101] unaligned access on connection of the first wireless client One of the crash logs had Interrupt Active while failing to emulate unaligned access - despite this patch. > [ECR ]: 0x00230400 => Misaligned r/w from 0x9e67a22b > [ 51.630000] [EFA ]: 0x9e67a22b > [ 51.630000] [BLINK ]: br_multicast_add_group+0x246/0x284 > [ 51.630000] [ERET ]: br_multicast_add_group+0xae/0x284 > [ 51.650000] [STAT32]: 0x0000020e : K A1 E2 E1 ^^^^ It seemed to me at the time that allowing this from kernel mode might require more things - like not allowing preemption or disabling further interrupts ? I looked in CRM but can't find more details - do u remember ! Can we try and reproduce that new-issue-after-patch or perhaps just add this patch as it is and deal with any fallouts later ? -Vineet > return 1; > > if (no_unaligned_warning) { >