From mboxrd@z Thu Jan 1 00:00:00 1970 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> 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" List-ID: 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.