From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: [PATCH v2] Linux VM workaround for Knights Landing A/D leak Date: Tue, 14 Jun 2016 14:13:48 -0700 Message-ID: References: <7FB15233-B347-4A87-9506-A9E10D331292@gmail.com> <1465923672-14232-1-git-send-email-lukasz.anaczkowski@intel.com> <57603DC0.9070607@linux.intel.com> <20160614193407.1470d998@lxorguk.ukuu.org.uk> <576052E0.3050408@linux.intel.com> <20160614191916.GI30015@pd.tnic> <4b2c481e-35ae-1cd6-ca58-1535bfef346c@zytor.com> <20160614204736.GL30015@pd.tnic> <20160614210255.GM30015@pd.tnic> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20160614210255.GM30015@pd.tnic> Sender: linux-kernel-owner@vger.kernel.org To: Borislav Petkov Cc: Dave Hansen , One Thousand Gnomes , Lukasz Anaczkowski , linux-kernel@vger.kernel.org, linux-mm@kvack.org, tglx@linutronix.de, mingo@redhat.com, ak@linux.intel.com, kirill.shutemov@linux.intel.com, mhocko@suse.com, akpm@linux-foundation.org, harish.srinivasappa@intel.com, lukasz.odzioba@intel.com, grzegorz.andrejczuk@intel.com, lukasz.daniluk@intel.com List-Id: linux-mm.kvack.org On June 14, 2016 2:02:55 PM PDT, Borislav Petkov wrote: >On Tue, Jun 14, 2016 at 01:54:25PM -0700, H. Peter Anvin wrote: >> There was that. It is still possible that we end up with NOP a JMP >> right before another JMP; we could perhaps make the patching code >> smarter and see if we have a JMP immediately after. > >Yeah, I still can't get reproduce that reliably - I remember seeing it >at some point but then dismissing it for another, higher-prio thing. >And >now the whole memory is hazy at best. > >But, you're giving me a great idea right now - I have this kernel >disassembler tool which dumps alternative sections already and I could >teach it to look for pathological cases around the patching sites and >scream. > >Something for my TODO list when I get a quiet moment. > >Thanks! We talked with the GCC people about always bias asm goto toward the first label even if followed by __builtin_unreachable(). I don't know if that happened; if so we should probably insert the unreachable for those versions of gcc only. -- Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.