From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 82A77B70EE for ; Tue, 19 Oct 2010 08:00:36 +1100 (EST) Subject: Re: PROBLEM: memory corrupting bug, bisected to 6dda9d55 From: Benjamin Herrenschmidt To: Mel Gorman In-Reply-To: <20101013144044.GS30667@csn.ul.ie> References: <20101009095718.1775.qmail@kosh.dhis.org> <20101011143022.GD30667@csn.ul.ie> <20101011140039.15a2c78d.akpm@linux-foundation.org> <20101013144044.GS30667@csn.ul.ie> Content-Type: text/plain; charset="UTF-8" Date: Tue, 19 Oct 2010 07:59:10 +1100 Message-ID: <1287435550.2341.7.camel@pasglop> Mime-Version: 1.0 Cc: Yinghai Lu , linux-kernel@vger.kernel.org, linux-mm@kvack.org, pacman@kosh.dhis.org, KOSAKI Motohiro , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Christoph Lameter List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2010-10-13 at 15:40 +0100, Mel Gorman wrote: > > This is somewhat contrived but I can see how it might happen even on one > CPU particularly if the L1 cache is virtual and is loose about checking > physical tags. > > > How sensitive/vulnerable is PPC32 to such things? > > > > I can not tell you specifically but if the above scenario is in any way > plausible, I believe it would depend on what sort of L1 cache the CPU > has. Maybe this particular version has a virtual cache with no physical > tagging and is depending on the OS not to make virtual aliasing mistakes. Nah, ppc doesn't have problems with cache aliases, it all looks physically tagged to the programmer (tho there's subtleties but none that explains the reported behaviour). Looks like real memory corruption to me. Cheers, Ben.