From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756368Ab3A2DGz (ORCPT ); Mon, 28 Jan 2013 22:06:55 -0500 Received: from e23smtp04.au.ibm.com ([202.81.31.146]:55377 "EHLO e23smtp04.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751801Ab3A2DGx (ORCPT ); Mon, 28 Jan 2013 22:06:53 -0500 Message-ID: <51073CC3.8030105@linux.vnet.ibm.com> Date: Tue, 29 Jan 2013 11:06:43 +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> In-Reply-To: <20130128105903.GA22871@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13012902-9264-0000-0000-00000312AF5E Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. So, i guess we can do the simple fix first.