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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 E141EC433DB for ; Tue, 26 Jan 2021 13:48:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9F6172223D for ; Tue, 26 Jan 2021 13:48:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404905AbhAZNsJ (ORCPT ); Tue, 26 Jan 2021 08:48:09 -0500 Received: from mga02.intel.com ([134.134.136.20]:7861 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405244AbhAZNrY (ORCPT ); Tue, 26 Jan 2021 08:47:24 -0500 IronPort-SDR: p9W/ZFS9zMtBBroU7k4wgd5u3b8RADYlSvDJBo98YTg3lcwDAG5mFs/yRKiAkJ92xxaIbc2LtG 3ZJcRCyWwduQ== X-IronPort-AV: E=McAfee;i="6000,8403,9875"; a="167000998" X-IronPort-AV: E=Sophos;i="5.79,375,1602572400"; d="scan'208";a="167000998" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jan 2021 05:45:38 -0800 IronPort-SDR: UC2V7B//+ecyvrs0PY7ylxbVBW9iLV8zAt9QDO7mFxVVVu+XeGwYluE2DT8SOF+J2rQe0ughHi 8qrtw7HOVSjQ== X-IronPort-AV: E=Sophos;i="5.79,375,1602572400"; d="scan'208";a="387831564" Received: from haotongw-mobl2.ccr.corp.intel.com (HELO localhost) ([10.255.28.153]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jan 2021 05:45:35 -0800 Date: Tue, 26 Jan 2021 21:45:31 +0800 From: Yu Zhang To: pbonzini@redhat.com Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, seanjc@google.com, vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org Subject: Re: [PATCH] KVM: x86/MMU: Do not check unsync status for root SP. Message-ID: <20210126134531.ctj326k3xwvmniwd@linux.intel.com> References: <20210116002100.17339-1-yu.c.zhang@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210116002100.17339-1-yu.c.zhang@linux.intel.com> User-Agent: NeoMutt/20171215 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Paolo, Any comments? Thanks! B.R. Yu On Sat, Jan 16, 2021 at 08:21:00AM +0800, Yu Zhang wrote: > In shadow page table, only leaf SPs may be marked as unsync. > And for non-leaf SPs, we use unsync_children to keep the number > of the unsynced children. In kvm_mmu_sync_root(), sp->unsync > shall always be zero for the root SP, hence no need to check it. > > Signed-off-by: Yu Zhang > --- > arch/x86/kvm/mmu/mmu.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 6d16481a..1a6bb03 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -3412,8 +3412,7 @@ void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu) > * mmu_need_write_protect() describe what could go wrong if this > * requirement isn't satisfied. > */ > - if (!smp_load_acquire(&sp->unsync) && > - !smp_load_acquire(&sp->unsync_children)) > + if (!smp_load_acquire(&sp->unsync_children)) > return; > > spin_lock(&vcpu->kvm->mmu_lock); > -- > 1.9.1 >