From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754192Ab3A2Hhg (ORCPT ); Tue, 29 Jan 2013 02:37:36 -0500 Received: from e23smtp05.au.ibm.com ([202.81.31.147]:41558 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751757Ab3A2Hhe (ORCPT ); Tue, 29 Jan 2013 02:37:34 -0500 Message-ID: <51077C33.60402@linux.vnet.ibm.com> Date: Tue, 29 Jan 2013 15:37:23 +0800 From: Xiao Guangrong User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Gleb Natapov CC: Takuya Yoshikawa , Alex Williamson , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/2] kvm: IOMMU read-only mapping support References: <20130124220027.11061.76400.stgit@bling.home> <20130125101704.b76b049d.yoshikawa_takuya_b1@lab.ntt.co.jp> <5101FBE8.9000206@linux.vnet.ibm.com> <20130128105903.GA22871@redhat.com> <51073CC3.8030105@linux.vnet.ibm.com> <20130129065049.GF22871@redhat.com> In-Reply-To: <20130129065049.GF22871@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13012907-1396-0000-0000-000002798C25 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/29/2013 02:50 PM, Gleb Natapov wrote: > On Tue, Jan 29, 2013 at 11:06:43AM +0800, Xiao Guangrong wrote: >> On 01/28/2013 06:59 PM, Gleb Natapov wrote: >>> On Fri, Jan 25, 2013 at 11:28:40AM +0800, Xiao Guangrong wrote: >>>> On 01/25/2013 09:17 AM, Takuya Yoshikawa wrote: >>>>> On Thu, 24 Jan 2013 15:03:57 -0700 >>>>> Alex Williamson wrote: >>>>> >>>>>> A couple patches to make KVM IOMMU support honor read-only mappings. >>>>>> This causes an un-map, re-map when the read-only flag changes and >>>>>> makes use of it when setting IOMMU attributes. Thanks, >>>>> >>>>> Looks good to me. >>>>> >>>>> I think I can naturally update my patch after this gets merged. >>>>> >>>> >>>> Please wait. >>>> >>>> The commit c972f3b1 changed the write-protect behaviour - it does >>>> wirte-protection only when dirty flag is set. >>>> [ I did not see this commit when we discussed the problem before. ] >>>> >>>> Further more, i notice that write-protect is not enough, when do sync >>>> shadow page: >>>> >>>> FNAME(sync_page): >>>> >>>> host_writable = sp->spt[i] & SPTE_HOST_WRITEABLE; >>>> >>>> set_spte(vcpu, &sp->spt[i], pte_access, >>>> PT_PAGE_TABLE_LEVEL, gfn, >>>> spte_to_pfn(sp->spt[i]), true, false, >>>> host_writable); >>>> >>>> It sets spte based on the old value that means the readonly flag check >>>> is missed. We need to call kvm_arch_flush_shadow_all under this case. >>> Why not just disallow changing memory region KVM_MEM_READONLY flag >>> without deleting the region? >> >> It will introduce some restriction when VM-sharing-mem is being implemented, >> but we need to do some optimization for it, at least, properly write-protect >> readonly pages (fix sync_page()) instead of zap_all_page. >> > What is VM-sharing-mem? Sharing memory between different guests. > >> So, i guess we can do the simple fix first. >> > By simple fix you mean calling kvm_arch_flush_shadow_all() on READONLY > flag change? Simply disallow READONLY flag changing.