From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965231Ab2LGSoG (ORCPT ); Fri, 7 Dec 2012 13:44:06 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44623 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755130Ab2LGSoE (ORCPT ); Fri, 7 Dec 2012 13:44:04 -0500 Date: Fri, 7 Dec 2012 13:44:01 -0500 From: Jason Baron To: Alex Williamson Cc: mtosatti@redhat.com, gleb@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH 02/10] kvm: Check userspace_addr when modifying a memory slot Message-ID: <20121207184400.GC13053@redhat.com> References: <20121206214722.24968.6043.stgit@bling.home> <20121206222037.24968.13698.stgit@bling.home> <20121207181725.GB13053@redhat.com> <1354905128.3224.98.camel@bling.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1354905128.3224.98.camel@bling.home> User-Agent: Mutt/1.5.20 (2009-12-10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 07, 2012 at 11:32:08AM -0700, Alex Williamson wrote: > On Fri, 2012-12-07 at 13:17 -0500, Jason Baron wrote: > > On Thu, Dec 06, 2012 at 03:20:37PM -0700, Alex Williamson wrote: > > > The API documents that only flags and guest physical memory space can > > > be modified on an existing slot, but we don't enforce that the > > > userspace address cannot be modified. Instead we just ignore it. > > > This means that a user may think they've successfully moved both the > > > guest and user addresses, when in fact only the guest address changed. > > > Check and error instead. > > > > > > Signed-off-by: Alex Williamson > > > --- > > > virt/kvm/kvm_main.c | 8 +++++++- > > > 1 file changed, 7 insertions(+), 1 deletion(-) > > > > > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > > index e426704..93213e1 100644 > > > --- a/virt/kvm/kvm_main.c > > > +++ b/virt/kvm/kvm_main.c > > > @@ -779,13 +779,19 @@ int __kvm_set_memory_region(struct kvm *kvm, > > > > > > r = -ENOMEM; > > > > > > - /* Allocate if a slot is being created */ > > > + /* > > > + * Allocate if a slot is being created. If modifying a slot, > > > + * the userspace_addr cannot change. > > > + */ > > > if (!old.npages) { > > > new.user_alloc = user_alloc; > > > new.userspace_addr = mem->userspace_addr; > > > > > > if (kvm_arch_create_memslot(&new, npages)) > > > goto out_free; > > > + } else if (mem->userspace_addr != old.userspace_addr) { > > > + r = -EINVAL; > > > + goto out_free; > > > } > > > > > > /* Allocate page dirty bitmap if needed */ > > > > > > > hmmm...does this mean that on a 'destroy', where npages is 0, the user > > has to set up userspace_addr correctly? If so, that would appear to be > > an unwanted change in semantics here. > > Good point, it does change that. We could make this be (npages && > mem->userspace_addr != old.userspace_addr) to avoid that case. Thanks, > > Alex > Yup, that works for me. Thanks, -Jason