Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0FCBC433EF for ; Tue, 23 Nov 2021 01:07:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231578AbhKWBKm (ORCPT ); Mon, 22 Nov 2021 20:10:42 -0500 Received: from mga12.intel.com ([192.55.52.136]:54361 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231174AbhKWBKl (ORCPT ); Mon, 22 Nov 2021 20:10:41 -0500 X-IronPort-AV: E=McAfee;i="6200,9189,10176"; a="214950573" X-IronPort-AV: E=Sophos;i="5.87,256,1631602800"; d="scan'208";a="214950573" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Nov 2021 17:07:33 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.87,256,1631602800"; d="scan'208";a="649751921" Received: from chaop.bj.intel.com (HELO localhost) ([10.240.192.101]) by fmsmga001.fm.intel.com with ESMTP; 22 Nov 2021 17:07:25 -0800 Date: Tue, 23 Nov 2021 09:06:39 +0800 From: Chao Peng To: "Kirill A. Shutemov" Cc: Wanpeng Li , jun.nakajima@intel.com, kvm@vger.kernel.org, david@redhat.com, qemu-devel@nongnu.org, "J . Bruce Fields" , dave.hansen@intel.com, "H . Peter Anvin" , ak@linux.intel.com, Jonathan Corbet , Joerg Roedel , x86@kernel.org, Hugh Dickins , Ingo Molnar , Borislav Petkov , luto@kernel.org, Thomas Gleixner , Andrew Morton , Jim Mattson , linux-mm@kvack.org, Sean Christopherson , susie.li@intel.com, Jeff Layton , linux-kernel@vger.kernel.org, john.ji@intel.com, Yu Zhang , linux-fsdevel@vger.kernel.org, Paolo Bonzini , Vitaly Kuznetsov , "Kirill A . Shutemov" Subject: Re: [RFC v2 PATCH 13/13] KVM: Enable memfd based page invalidation/fallocate Message-ID: <20211123010639.GA32088@chaop.bj.intel.com> Reply-To: Chao Peng References: <20211119134739.20218-1-chao.p.peng@linux.intel.com> <20211119134739.20218-14-chao.p.peng@linux.intel.com> <20211122141647.3pcsywilrzcoqvbf@box.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211122141647.3pcsywilrzcoqvbf@box.shutemov.name> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 22, 2021 at 05:16:47PM +0300, Kirill A. Shutemov wrote: > On Fri, Nov 19, 2021 at 09:47:39PM +0800, Chao Peng wrote: > > Since the memory backing store does not get notified when VM is > > destroyed so need check if VM is still live in these callbacks. > > > > Signed-off-by: Yu Zhang > > Signed-off-by: Chao Peng > > --- > > virt/kvm/memfd.c | 22 ++++++++++++++++++++++ > > 1 file changed, 22 insertions(+) > > > > diff --git a/virt/kvm/memfd.c b/virt/kvm/memfd.c > > index bd930dcb455f..bcfdc685ce22 100644 > > --- a/virt/kvm/memfd.c > > +++ b/virt/kvm/memfd.c > > @@ -12,16 +12,38 @@ > > #include > > const static struct guest_mem_ops *memfd_ops; > > > > +static bool vm_is_dead(struct kvm *vm) > > +{ > > + struct kvm *kvm; > > + > > + list_for_each_entry(kvm, &vm_list, vm_list) { > > + if (kvm == vm) > > + return false; > > + } > > I don't think this is enough. The struct kvm can be freed and re-allocated > from the slab and this function will give false-negetive. Right. > > Maybe the kvm has to be tagged with a sequential id that incremented every > allocation. This id can be checked here. Sounds like a sequential id will be needed, no existing fields in struct kvm can work for this. > > > + > > + return true; > > +} > > -- > Kirill A. Shutemov