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, URIBL_BLOCKED,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 85BD1C433DF for ; Wed, 3 Jun 2020 02:24:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 663C0207F9 for ; Wed, 3 Jun 2020 02:24:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725810AbgFCCYQ (ORCPT ); Tue, 2 Jun 2020 22:24:16 -0400 Received: from mga02.intel.com ([134.134.136.20]:14630 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725780AbgFCCYQ (ORCPT ); Tue, 2 Jun 2020 22:24:16 -0400 IronPort-SDR: Fg+aPrISzAGDr4jHS/AMXPVLmwb8wvsas1LMiSnZkloEz9OapG+NxZCIzrdoCnSbW+hxq76/Vy mGu8itVzYjHg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Jun 2020 19:24:15 -0700 IronPort-SDR: tNy2nn62cX3ruc8KIngYK08o7rjpTA3Knoty3ydGbRuVfgxdznpVxe1I53Mt+ZlWcdjOoZiZQI zNVD3hHpfkBA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,466,1583222400"; d="scan'208";a="312455531" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.152]) by FMSMGA003.fm.intel.com with ESMTP; 02 Jun 2020 19:24:15 -0700 Date: Tue, 2 Jun 2020 19:24:14 -0700 From: Sean Christopherson To: Jim Mattson Cc: kvm list , Paolo Bonzini , Liran Alon , Oliver Upton , Peter Shier Subject: Re: [PATCH v3 3/4] kvm: vmx: Add last_cpu to struct vcpu_vmx Message-ID: <20200603022414.GA24364@linux.intel.com> References: <20200601222416.71303-1-jmattson@google.com> <20200601222416.71303-4-jmattson@google.com> <20200602012139.GF21661@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Tue, Jun 02, 2020 at 10:33:51AM -0700, Jim Mattson wrote: > On Mon, Jun 1, 2020 at 6:21 PM Sean Christopherson > wrote: > > > > On Mon, Jun 01, 2020 at 03:24:15PM -0700, Jim Mattson wrote: > > > As we already do in svm, record the last logical processor on which a > > > vCPU has run, so that it can be communicated to userspace for > > > potential hardware errors. > > > > > > Signed-off-by: Jim Mattson > > > Reviewed-by: Oliver Upton > > > Reviewed-by: Peter Shier > > > --- > > > arch/x86/kvm/vmx/vmx.c | 1 + > > > arch/x86/kvm/vmx/vmx.h | 3 +++ > > > 2 files changed, 4 insertions(+) > > > > > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > > > index 170cc76a581f..42856970d3b8 100644 > > > --- a/arch/x86/kvm/vmx/vmx.c > > > +++ b/arch/x86/kvm/vmx/vmx.c > > > @@ -6730,6 +6730,7 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu) > > > if (vcpu->arch.cr2 != read_cr2()) > > > write_cr2(vcpu->arch.cr2); > > > > > > + vmx->last_cpu = vcpu->cpu; > > > > This is redundant in the EXIT_FASTPATH_REENTER_GUEST case. Setting it > > before reenter_guest is technically wrong if emulation_required is true, but > > that doesn't seem like it'd be an issue in practice. > > I really would like to capture the last logical processor to execute > VMLAUNCH/VMRESUME (or VMRUN on the AMD side) on behalf of this vCPU. Does it matter though? The flows that consume the variable are all directly in the VM-Exit path. > > > vmx->fail = __vmx_vcpu_run(vmx, (unsigned long *)&vcpu->arch.regs, > > > vmx->loaded_vmcs->launched); > > > > > > diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h > > > index 672c28f17e49..8a1e833cf4fb 100644 > > > --- a/arch/x86/kvm/vmx/vmx.h > > > +++ b/arch/x86/kvm/vmx/vmx.h > > > @@ -302,6 +302,9 @@ struct vcpu_vmx { > > > u64 ept_pointer; > > > > > > struct pt_desc pt_desc; > > > + > > > + /* which host CPU was used for running this vcpu */ > > > + unsigned int last_cpu; > > > > Why not put this in struct kvm_vcpu_arch? I'd also vote to name it > > last_run_cpu, as last_cpu is super misleading. > > I think last_run_cpu may also be misleading, since in the cases of > interest, nothing actually 'ran.' Maybe last_attempted_vmentry_cpu? Ya, that thought crossed my mind as well. > > And if it's in arch, what about setting it vcpu_enter_guest? > > As you point out above, this isn't entirely accurate. (But that's the > way we roll in kvm, isn't it? :-) As an alternative to storing the last run/attempted CPU, what about moving the "bad VM-Exit" detection into handle_exit_irqoff, or maybe a new hook that is called after IRQs are enabled but before preemption is enabled, e.g. detect_bad_exit or something? All of the paths in patch 4/4 can easily be moved out of handle_exit. VMX would require a little bit of refacotring for it's "no handler" check, but that should be minor.