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[14.202.194.140]) by smtp.gmail.com with ESMTPSA id b14-v6sm35131010pfc.178.2018.09.18.18.03.40 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 18 Sep 2018 18:03:41 -0700 (PDT) Date: Wed, 19 Sep 2018 11:03:37 +1000 From: Balbir Singh To: "Woodhouse, David" Cc: "torvalds@linux-foundation.org" , "konrad.wilk@oracle.com" , "juerg.haefliger@hpe.com" , "deepa.srinivasan@oracle.com" , "jmattson@google.com" , "andrew.cooper3@citrix.com" , "linux-kernel@vger.kernel.org" , "boris.ostrovsky@oracle.com" , "linux-mm@kvack.org" , "tglx@linutronix.de" , "joao.m.martins@oracle.com" , "pradeep.vincent@oracle.com" , "ak@linux.intel.com" , "khalid.aziz@oracle.com" , "kanth.ghatraju@oracle.com" , "liran.alon@oracle.com" , "keescook@google.com" , "jsteckli@os.inf.tu-dresden.de" , "kernel-hardening@lists.openwall.com" , "chris.hyser@oracle.com" , "tyhicks@canonical.com" , "john.haxby@oracle.com" , "jcm@redhat.com" Subject: Re: Redoing eXclusive Page Frame Ownership (XPFO) with isolated CPUs in mind (for KVM to isolate its guests per CPU) Message-ID: <20180919010337.GC8537@350D> References: <20180820212556.GC2230@char.us.oracle.com> <1534801939.10027.24.camel@amazon.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1534801939.10027.24.camel@amazon.co.uk> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 20, 2018 at 09:52:19PM +0000, Woodhouse, David wrote: > On Mon, 2018-08-20 at 14:48 -0700, Linus Torvalds wrote: > > > > Of course, after the long (and entirely unrelated) discussion about > > the TLB flushing bug we had, I'm starting to worry about my own > > competence, and maybe I'm missing something really fundamental, and > > the XPFO patches do something else than what I think they do, or my > > "hey, let's use our Meltdown code" idea has some fundamental weakness > > that I'm missing. > > The interesting part is taking the user (and other) pages out of the > kernel's 1:1 physmap. > > It's the *kernel* we don't want being able to access those pages, > because of the multitude of unfixable cache load gadgets. I am missing why we need this since the kernel can't access (SMAP) unless we go through to the copy/to/from interface or execute any of the user pages. Is it because of the dependency on the availability of those features? Balbir Singh. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f198.google.com (mail-pg1-f198.google.com [209.85.215.198]) by kanga.kvack.org (Postfix) with ESMTP id 2DE458E0001 for ; Tue, 18 Sep 2018 21:03:44 -0400 (EDT) Received: by mail-pg1-f198.google.com with SMTP id d132-v6so1611475pgc.22 for ; Tue, 18 Sep 2018 18:03:44 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id t190-v6sor1819369pgd.413.2018.09.18.18.03.42 for (Google Transport Security); Tue, 18 Sep 2018 18:03:42 -0700 (PDT) Date: Wed, 19 Sep 2018 11:03:37 +1000 From: Balbir Singh Subject: Re: Redoing eXclusive Page Frame Ownership (XPFO) with isolated CPUs in mind (for KVM to isolate its guests per CPU) Message-ID: <20180919010337.GC8537@350D> References: <20180820212556.GC2230@char.us.oracle.com> <1534801939.10027.24.camel@amazon.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1534801939.10027.24.camel@amazon.co.uk> Sender: owner-linux-mm@kvack.org List-ID: To: "Woodhouse, David" Cc: "torvalds@linux-foundation.org" , "konrad.wilk@oracle.com" , "juerg.haefliger@hpe.com" , "deepa.srinivasan@oracle.com" , "jmattson@google.com" , "andrew.cooper3@citrix.com" , "linux-kernel@vger.kernel.org" , "boris.ostrovsky@oracle.com" , "linux-mm@kvack.org" , "tglx@linutronix.de" , "joao.m.martins@oracle.com" , "pradeep.vincent@oracle.com" , "ak@linux.intel.com" , "khalid.aziz@oracle.com" , "kanth.ghatraju@oracle.com" , "liran.alon@oracle.com" , "keescook@google.com" , "jsteckli@os.inf.tu-dresden.de" , "kernel-hardening@lists.openwall.com" , "chris.hyser@oracle.com" , "tyhicks@canonical.com" , "john.haxby@oracle.com" , "jcm@redhat.com" On Mon, Aug 20, 2018 at 09:52:19PM +0000, Woodhouse, David wrote: > On Mon, 2018-08-20 at 14:48 -0700, Linus Torvalds wrote: > > > > Of course, after the long (and entirely unrelated) discussion about > > the TLB flushing bug we had, I'm starting to worry about my own > > competence, and maybe I'm missing something really fundamental, and > > the XPFO patches do something else than what I think they do, or my > > "hey, let's use our Meltdown code" idea has some fundamental weakness > > that I'm missing. > > The interesting part is taking the user (and other) pages out of the > kernel's 1:1 physmap. > > It's the *kernel* we don't want being able to access those pages, > because of the multitude of unfixable cache load gadgets. I am missing why we need this since the kernel can't access (SMAP) unless we go through to the copy/to/from interface or execute any of the user pages. Is it because of the dependency on the availability of those features? Balbir Singh.