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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 D4952C3F2CD for ; Fri, 28 Feb 2020 14:59:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B0D3D246AE for ; Fri, 28 Feb 2020 14:59:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727027AbgB1O7p (ORCPT ); Fri, 28 Feb 2020 09:59:45 -0500 Received: from mga09.intel.com ([134.134.136.24]:36391 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726788AbgB1O7o (ORCPT ); Fri, 28 Feb 2020 09:59:44 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Feb 2020 06:59:44 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,496,1574150400"; d="scan'208";a="437437616" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.202]) by fmsmga005.fm.intel.com with ESMTP; 28 Feb 2020 06:59:43 -0800 Date: Fri, 28 Feb 2020 06:59:43 -0800 From: Sean Christopherson To: Paolo Bonzini Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] KVM: VMX: Always VMCLEAR in-use VMCSes during crash with kexec support Message-ID: <20200228145942.GA2329@linux.intel.com> References: <20200227223047.13125-1-sean.j.christopherson@intel.com> <20200227223047.13125-2-sean.j.christopherson@intel.com> <9edc8cef-9aa4-11ca-f8f2-a1fea990b87e@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9edc8cef-9aa4-11ca-f8f2-a1fea990b87e@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Feb 28, 2020 at 11:16:10AM +0100, Paolo Bonzini wrote: > On 27/02/20 23:30, Sean Christopherson wrote: > > -void loaded_vmcs_init(struct loaded_vmcs *loaded_vmcs) > > +void loaded_vmcs_init(struct loaded_vmcs *loaded_vmcs, bool in_use) > > { > > vmcs_clear(loaded_vmcs->vmcs); > > if (loaded_vmcs->shadow_vmcs && loaded_vmcs->launched) > > vmcs_clear(loaded_vmcs->shadow_vmcs); > > + > > + if (in_use) { > > + list_del(&loaded_vmcs->loaded_vmcss_on_cpu_link); > > + > > + /* > > + * Ensure deleting loaded_vmcs from its current percpu list > > + * completes before setting loaded_vmcs->vcpu to -1, otherwise > > + * a different cpu can see vcpu == -1 first and add loaded_vmcs > > + * to its percpu list before it's deleted from this cpu's list. > > + * Pairs with the smp_rmb() in vmx_vcpu_load_vmcs(). > > + */ > > + smp_wmb(); > > + } > > + > > I'd like to avoid the new in_use argument and, also, I think it's a > little bit nicer to always invoke the memory barrier. Even though we > use "asm volatile" for vmclear and therefore the compiler is already > taken care of, in principle it's more correct to order the ->cpu write > against vmclear's. Completely agree on all points. I wanted to avoid in_use as well, but it didn't occur to me to use list_empty()... > This gives the following patch on top: Looks good. > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index c9d6152e7a4d..77a64110577b 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -656,25 +656,24 @@ static int vmx_set_guest_msr(struct vcpu_vmx *vmx, struct shared_msr_entry *msr, > return ret; > } > > -void loaded_vmcs_init(struct loaded_vmcs *loaded_vmcs, bool in_use) > +void loaded_vmcs_init(struct loaded_vmcs *loaded_vmcs) > { > vmcs_clear(loaded_vmcs->vmcs); > if (loaded_vmcs->shadow_vmcs && loaded_vmcs->launched) > vmcs_clear(loaded_vmcs->shadow_vmcs); > > - if (in_use) { > + if (!list_empty(&loaded_vmcs->loaded_vmcss_on_cpu_link)) > list_del(&loaded_vmcs->loaded_vmcss_on_cpu_link); > > - /* > - * Ensure deleting loaded_vmcs from its current percpu list > - * completes before setting loaded_vmcs->vcpu to -1, otherwise > - * a different cpu can see vcpu == -1 first and add loaded_vmcs > - * to its percpu list before it's deleted from this cpu's list. > - * Pairs with the smp_rmb() in vmx_vcpu_load_vmcs(). > - */ > - smp_wmb(); > - } > - > + /* > + * Ensure all writes to loaded_vmcs, including deleting it > + * from its current percpu list, complete before setting > + * loaded_vmcs->vcpu to -1; otherwise,, a different cpu can > + * see vcpu == -1 first and add loaded_vmcs to its percpu > + * list before it's deleted from this cpu's list. Pairs > + * with the smp_rmb() in vmx_vcpu_load_vmcs(). > + */ > + smp_wmb(); > loaded_vmcs->cpu = -1; > loaded_vmcs->launched = 0; > } > @@ -701,7 +700,7 @@ static void __loaded_vmcs_clear(void *arg) > if (per_cpu(current_vmcs, cpu) == loaded_vmcs->vmcs) > per_cpu(current_vmcs, cpu) = NULL; > > - loaded_vmcs_init(loaded_vmcs, true); > + loaded_vmcs_init(loaded_vmcs); > } > > void loaded_vmcs_clear(struct loaded_vmcs *loaded_vmcs) > @@ -2568,7 +2567,8 @@ int alloc_loaded_vmcs(struct loaded_vmcs *loaded_vmcs) > > loaded_vmcs->shadow_vmcs = NULL; > loaded_vmcs->hv_timer_soft_disabled = false; > - loaded_vmcs_init(loaded_vmcs, false); > + INIT_LIST_HEAD(&loaded_vmcs->loaded_vmcss_on_cpu_link); > + loaded_vmcs_init(loaded_vmcs); > > if (cpu_has_vmx_msr_bitmap()) { > loaded_vmcs->msr_bitmap = (unsigned long *) > > Paolo >