From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752769Ab2HNOAk (ORCPT ); Tue, 14 Aug 2012 10:00:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53617 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752227Ab2HNOAi (ORCPT ); Tue, 14 Aug 2012 10:00:38 -0400 Message-ID: <502A5A01.6040505@redhat.com> Date: Tue, 14 Aug 2012 17:00:33 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120717 Thunderbird/14.0 MIME-Version: 1.0 To: Marcelo Tosatti CC: Xiao Guangrong , LKML , KVM Subject: Re: [PATCH v5 00/12] KVM: introduce readonly memslot References: <5020E423.9080004@linux.vnet.ibm.com> <20120810181422.GA14892@amt.cnet> In-Reply-To: <20120810181422.GA14892@amt.cnet> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/10/2012 09:14 PM, Marcelo Tosatti wrote: > On Tue, Aug 07, 2012 at 05:47:15PM +0800, Xiao Guangrong wrote: >> Changelog: >> - introduce KVM_PFN_ERR_RO_FAULT instead of dummy page >> - introduce KVM_HVA_ERR_BAD and optimize error hva indicators >> >> The test case can be found at: >> http://lkml.indiana.edu/hypermail/linux/kernel/1207.2/00819/migrate-perf.tar.bz2 >> >> In current code, 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. >> >> As Avi's suggestion, We introduce readonly memory region to map ROM/ROMD >> to the guest, read access is happy for readonly memslot, write access on >> readonly memslot will cause KVM_EXIT_MMIO exit. > > Memory slots whose QEMU mapping is write protected is supported > today, as long as there are no write faults. > > What prevents the use of mmap(!MAP_WRITE) to handle read-only memslots > again? Userspace may want to modify the ROM (for example, when programming a flash device). It is also possible to map an hva range rw through one slot and ro through another. -- error compiling committee.c: too many arguments to function