From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754043Ab2EVFbP (ORCPT ); Tue, 22 May 2012 01:31:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:14716 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753528Ab2EVFbN (ORCPT ); Tue, 22 May 2012 01:31:13 -0400 Date: Tue, 22 May 2012 08:31:10 +0300 From: Gleb Natapov To: Marcelo Tosatti Cc: Xiao Guangrong , Avi Kivity , LKML , KVM Subject: Re: [PATCH] KVM: fix async page fault working for readonly mapping Message-ID: <20120522053110.GT10209@redhat.com> References: <4FB9E499.2010505@linux.vnet.ibm.com> <20120521080856.GS10209@redhat.com> <4FB9F9B6.50101@linux.vnet.ibm.com> <20120521193041.GA25940@amt.cnet> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120521193041.GA25940@amt.cnet> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 21, 2012 at 04:30:41PM -0300, Marcelo Tosatti wrote: > On Mon, May 21, 2012 at 04:15:50PM +0800, Xiao Guangrong wrote: > > On 05/21/2012 04:08 PM, Gleb Natapov wrote: > > > > > On Mon, May 21, 2012 at 02:45:45PM +0800, Xiao Guangrong wrote: > > >> If we map a readonly memory space from host to guest and the page is > > >> not currently mapped in the host, we will get a fault-pfn and async > > >> is not allowed, then the vm will crash > > >> > > > Why would we want to map a readonly memory space from host to guest? > > > We may want to do it to support memory semantics on read and mmio on > > > write, but do not right now unless something changed while I was not > > > looking. > > > > > > Some test cases in kvm-unit-tests and the benchmark i am writing for KVM > > need map the function on host to guest. > > Or ROM. Or read-only mappings of IVSHMEM (which don't exist yet). True. KVM should ignore writes to such areas, not kill a guest. Is this how the code works today? -- Gleb.