From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759470Ab2IKOye (ORCPT ); Tue, 11 Sep 2012 10:54:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46683 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755451Ab2IKOyc (ORCPT ); Tue, 11 Sep 2012 10:54:32 -0400 Date: Tue, 11 Sep 2012 11:39:01 -0300 From: Marcelo Tosatti To: Avi Kivity Cc: Xiao Guangrong , LKML , KVM Subject: Re: [PATCH v6 12/12] KVM: indicate readonly access fault Message-ID: <20120911143901.GA11792@amt.cnet> References: <5032F8FD.2020306@linux.vnet.ibm.com> <5032FA78.9040405@linux.vnet.ibm.com> <5034CB60.30107@redhat.com> <5034D4E3.2080801@linux.vnet.ibm.com> <5048AE96.3050909@redhat.com> <5049C4D7.50101@linux.vnet.ibm.com> <20120910223140.GA24275@amt.cnet> <504F01DE.20505@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <504F01DE.20505@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 11, 2012 at 12:18:22PM +0300, Avi Kivity wrote: > > The same can happen with slot deletion, for example. > > > > Userspace (which performed the modification which can result in faults > > to non-existant/read-only/.../new-tag memslot), must handle the faults > > properly or avoid the possibility for reference to memslot information > > from the past. > > > > I think its worthwhile to add a note about this in the API > > documentation: "The user of this interface is responsible for handling > > references to stale memslot information, either by handling > > exit notifications which reference stale memslot information or not > > allowing these notifications to exist by stopping all vcpus in userspace > > before performing modifications to the memslots map". > > Or we can drop the new interface and rely on userspace to perform the > lookup under its own locking rules. > > It's slow, but writes to ROM or ROM/device are rare anyway. Lookup what information?