From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Ahern Date: Mon, 23 Mar 2015 17:34:34 +0000 Subject: Re: 4.0.0-rc4: panic in free_block Message-Id: <55104EAA.4060607@oracle.com> List-Id: 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> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: David Miller Cc: torvalds@linux-foundation.org, sparclinux@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpicco@meloft.net 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