From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753086AbbCWRel (ORCPT ); Mon, 23 Mar 2015 13:34:41 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:43831 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752158AbbCWRej (ORCPT ); Mon, 23 Mar 2015 13:34:39 -0400 Message-ID: <55104EAA.4060607@oracle.com> Date: Mon, 23 Mar 2015 11:34:34 -0600 From: David Ahern User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: David Miller CC: torvalds@linux-foundation.org, sparclinux@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpicco@meloft.net Subject: Re: 4.0.0-rc4: panic in free_block References: <550F5852.5020405@oracle.com> <20150322.220024.1171832215344978787.davem@davemloft.net> <20150322.221906.1670737065885267482.davem@davemloft.net> <20150323.122530.812870422534676208.davem@davemloft.net> In-Reply-To: <20150323.122530.812870422534676208.davem@davemloft.net> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/23/15 10:25 AM, David Miller wrote: > [PATCH] sparc64: Fix several bugs in memmove(). > > Firstly, handle zero length calls properly. Believe it or not there > are a few of these happening during early boot. > > Next, we can't just drop to a memcpy() call in the forward copy case > where dst <= src. The reason is that the cache initializing stores > used in the Niagara memcpy() implementations can end up clearing out > cache lines before we've sourced their original contents completely. > > For example, considering NG4memcpy, the main unrolled loop begins like > this: > > load src + 0x00 > load src + 0x08 > load src + 0x10 > load src + 0x18 > load src + 0x20 > store dst + 0x00 > > Assume dst is 64 byte aligned and let's say that dst is src - 8 for > this memcpy() call. That store at the end there is the one to the > first line in the cache line, thus clearing the whole line, which thus > clobbers "src + 0x28" before it even gets loaded. > > To avoid this, just fall through to a simple copy only mildly > optimized for the case where src and dst are 8 byte aligned and the > length is a multiple of 8 as well. We could get fancy and call > GENmemcpy() but this is good enough for how this thing is actually > used. > > Reported-by: David Ahern > Reported-by: Bob Picco > Signed-off-by: David S. Miller seems like a formality at this point, but this resolves the panic on the M7-based ldom and baremetal. The T5-8 failed to boot, but it could be a different problem. Thanks for the fast turnaround, David