From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-x234.google.com (mail-pa0-x234.google.com [IPv6:2607:f8b0:400e:c03::234]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority" (not verified)) by ozlabs.org (Postfix) with ESMTPS id C4C922C00AA for ; Mon, 3 Jun 2013 04:19:20 +1000 (EST) Received: by mail-pa0-f52.google.com with SMTP id bg2so577758pad.25 for ; Sun, 02 Jun 2013 11:19:17 -0700 (PDT) Date: Sun, 2 Jun 2013 11:19:17 -0700 (PDT) From: Hugh Dickins To: "Aneesh Kumar K.V" Subject: Re: 3.10-rc ppc64 corrupts usermem when swapping In-Reply-To: <8738t1c6y7.fsf@linux.vnet.ibm.com> Message-ID: References: <1369897236.3928.93.camel@pasglop> <87vc60na89.fsf@linux.vnet.ibm.com> <1369902786.3928.94.camel@pasglop> <1369978262.3928.111.camel@pasglop> <87ppw7mrx7.fsf@linux.vnet.ibm.com> <1370038982.3928.147.camel@pasglop> <8738t1c6y7.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: linuxppc-dev@lists.ozlabs.org, Benjamin Herrenschmidt , Paul Mackerras , Anton Blanchard , David Gibson List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Sun, 2 Jun 2013, Aneesh Kumar K.V wrote: > Benjamin Herrenschmidt writes: > > On Fri, 2013-05-31 at 14:45 +0530, Aneesh Kumar K.V wrote: > > > >> > The patch you are running on is what I'll send to Linus for 3.10 (+/- > >> > cosmetics). Aneesh second patch is a much larger rework which will be > >> > needed for THP but that will wait for 3.11. I'm happy for you to test it > >> > but I first want to make sure it's solid with the 3.10 fix :-) > > > > BTW. One concern I still have is that Hugh identified the bad commit > > to be: > > > > 7e74c3921ad9610c0b49f28b8fc69f7480505841 > > "powerpc: Fix hpte_decode to use the correct decoding for page sizes". > > > > However, you introduce the return on HPTE not found earlier, in > > > > b1022fbd293564de91596b8775340cf41ad5214c > > "powerpc: Decode the pte-lp-encoding bits correctly." > > > > So while I'm still happy with the current band-aid for 3.10 and am > > about to send it to Linus, the above *does* seem to indicate that > > there is also something wrong with the "Fix hpte_decode..." commit, > > which might not actually get the page size right... > > > > Can you investigate ? > > 7e74c3921ad9610c0b49f28b8fc69f7480505841 > "powerpc: Fix hpte_decode to use the correct decoding for page sizes" > changes should only impact hpte_decode. We don't change the details > of hpte_actual_psize at all in this patch. That means we should see a > difference only with kexec right ?. > > Hugh, > > Will you be able to double check whether > 7e74c3921ad9610c0b49f28b8fc69f7480505841 is the bad commit. The one > before that is what we changed in the patch that fixed your problem. You are absolutely right. I just set b1022fbd29 going, expecting to answer you tomorrow: but got a Segmentation fault in 20 minutes (quicker than ever seen before). It looks as if I was running some other kernel for the last stage of my bisection: I can't see how that came about, but it's not very interesting now - you got it right. Prior to trying that, I had been running your second patch, 9f70fd8cfe, and that tested out successfully for 50 hours before I stopped it. Hugh