From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753870Ab2FSHUf (ORCPT ); Tue, 19 Jun 2012 03:20:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51612 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751878Ab2FSHUd (ORCPT ); Tue, 19 Jun 2012 03:20:33 -0400 Date: Tue, 19 Jun 2012 10:20:30 +0300 From: Gleb Natapov To: Marcelo Tosatti Cc: Avi Kivity , Xiao Guangrong , LKML , KVM Subject: Re: [PATCH v3 6/6] KVM: introduce readonly memslot Message-ID: <20120619072030.GM6533@redhat.com> References: <4FD6ADA6.40008@linux.vnet.ibm.com> <4FD6AE3B.9020508@linux.vnet.ibm.com> <20120616021150.GA3870@amt.cnet> <4FDEF9D2.3000909@redhat.com> <20120618202505.GA3650@amt.cnet> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120618202505.GA3650@amt.cnet> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 18, 2012 at 05:25:05PM -0300, Marcelo Tosatti wrote: > On Mon, Jun 18, 2012 at 12:50:10PM +0300, Avi Kivity wrote: > > On 06/16/2012 05:11 AM, Marcelo Tosatti wrote: > > > > > > Can you introduce a separate exit reason, say KVM_EXIT_READ_FAULT, with > > > information about the fault? > > > > I think you mean WRITE_FAULT. > > Yes. > > > But what's wrong with the normal mmio exit? > > It is necessary to perform an address->mmio region lookup, to verify > whether the mmio exit is due to an actual mmio (no memory slot) or from > a write access to a write protected slot. That information is readily > available in the kernel but is lost if the mmio exit is used to transmit > the information. > Why is it necessary though? Write access to a write protected slot is MMIO by (our) definition. > Moreover, i'd argue the uses are different: one is an mmio emulation > exit, the other is more like handling a pagefault in qemu. > What do you mean by "handling a pagefault in qemu"? -- Gleb.