From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 108D9C432C0 for ; Mon, 2 Dec 2019 19:30:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D657720833 for ; Mon, 2 Dec 2019 19:30:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728047AbfLBTaa (ORCPT ); Mon, 2 Dec 2019 14:30:30 -0500 Received: from mga03.intel.com ([134.134.136.65]:54608 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727586AbfLBTa3 (ORCPT ); Mon, 2 Dec 2019 14:30:29 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 02 Dec 2019 11:30:28 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,270,1571727600"; d="scan'208";a="242075360" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.41]) by fmsmga002.fm.intel.com with ESMTP; 02 Dec 2019 11:30:28 -0800 Date: Mon, 2 Dec 2019 11:30:27 -0800 From: Sean Christopherson To: Peter Xu Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini , "Dr . David Alan Gilbert" , Vitaly Kuznetsov Subject: Re: [PATCH RFC 03/15] KVM: Add build-time error check on kvm_run size Message-ID: <20191202193027.GH4063@linux.intel.com> References: <20191129213505.18472-1-peterx@redhat.com> <20191129213505.18472-4-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191129213505.18472-4-peterx@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 29, 2019 at 04:34:53PM -0500, Peter Xu wrote: > It's already going to reach 2400 Bytes (which is over half of page > size on 4K page archs), so maybe it's good to have this build-time > check in case it overflows when adding new fields. Please explain why exceeding PAGE_SIZE is a bad thing. I realize it's almost absurdly obvious when looking at the code, but a) the patch itself does not provide that context and b) the changelog should hold up on its own, e.g. in a mostly hypothetical case where the allocation of vcpu->run were changed to something else. > Signed-off-by: Peter Xu > --- > virt/kvm/kvm_main.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 8f8940cc4b84..681452d288cd 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -352,6 +352,8 @@ int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id) > } > vcpu->run = page_address(page); > > + BUILD_BUG_ON(sizeof(struct kvm_run) > PAGE_SIZE); > + > kvm_vcpu_set_in_spin_loop(vcpu, false); > kvm_vcpu_set_dy_eligible(vcpu, false); > vcpu->preempted = false; > -- > 2.21.0 >