From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v2] KVM: introduce readonly memory region Date: Thu, 24 May 2012 13:33:25 +0300 Message-ID: <4FBE0E75.8080503@redhat.com> References: <4FBDFE52.5090902@linux.vnet.ibm.com> <20120524095938.GX10209@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Xiao Guangrong , Marcelo Tosatti , LKML , KVM To: Gleb Natapov Return-path: In-Reply-To: <20120524095938.GX10209@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 05/24/2012 12:59 PM, Gleb Natapov wrote: > On Thu, May 24, 2012 at 05:24:34PM +0800, Xiao Guangrong wrote: >> 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 >> >> Address Avi's idea, we introduce readonly memory region to map ROM/ROMD >> to the guest >> > As far as I can tell this implements only ROMD. i.e write access to read > only slot will generate IO exit. Which userspace can then ignore. The question is whether writes to ROM are frequent, and whether the performance in that case matters. -- error compiling committee.c: too many arguments to function