From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH/PFC 0/2] s390 host support Date: Sun, 29 Apr 2007 15:27:21 +0300 Message-ID: <46348F29.4060505@qumranet.com> References: <1177681224.5770.20.camel@cotte.boeblingen.de.ibm.com> <4632E94C.20904@qumranet.com> <4633099D.3020709@de.ibm.com> <463461B1.7060406@qumranet.com> <4634726F.10705@de.ibm.com> <463477EE.3000406@qumranet.com> <20070429121351.GA8254@osiris.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: carsteno-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org, "kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org" , Christian Borntraeger , mschwid2-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org To: Heiko Carstens Return-path: In-Reply-To: <20070429121351.GA8254-5VkHqLvV2o3MbYB6QlFGEg@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Heiko Carstens wrote: >> Nested page tables/extended page tables also provide this facility, with >> some caveats: >> >> - on 32-bit hosts (or 64-bit hosts with 32-bit userspace), host >> userspace virtual address space is not enough to contain the guest >> physical address space. >> - there is no way to protect the host userspace from the guest >> > > Sorry, but are you saying that it is currently possible to access > (read and/or write) host userspace address space from the guest? > No. First, we don't yet have support for npt (I'm promised a patch by AMD). Second, the way I first planned it, guest physical and host userspace would be completely unrelated address spaces, with guest physical mmap()ed into host userspace. This is how non-npt is implemented right now. Third, our conversation gave rise to an idea of how to implement guest physical as a strict subset of host userspace. This (a) preserves isolation, and (b) allows the Linux mm to operate unmodified [1] on the guest ptes. I was being unclear: npt/ept _allows_ one to do this, but you're not _forced_ to. The strict subset thing is a kind of a mix between the two that still preserves isolation. [1] We'd still need to teach it how to invalidate guest tlb entries, unfortunately. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/