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=-11.3 required=3.0 tests=BAYES_00, 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 93E81C43466 for ; Mon, 21 Sep 2020 16:08:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 41ADB20708 for ; Mon, 21 Sep 2020 16:08:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727231AbgIUQIO (ORCPT ); Mon, 21 Sep 2020 12:08:14 -0400 Received: from mga03.intel.com ([134.134.136.65]:40028 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726419AbgIUQIO (ORCPT ); Mon, 21 Sep 2020 12:08:14 -0400 IronPort-SDR: RRItxq4VBejbUEyL0MDkp5sSFcvExM/WLkAlY4XnW/s3cDPPsNSCQIMyyKFASzhP2RHZhAdFx6 5TSO6tcef5kw== X-IronPort-AV: E=McAfee;i="6000,8403,9751"; a="160479295" X-IronPort-AV: E=Sophos;i="5.77,287,1596524400"; d="scan'208";a="160479295" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Sep 2020 09:08:14 -0700 IronPort-SDR: 051PsSzC0eVf6k01q0l2RoBVBkMCGYIYlRA1kzvgHSuXW/D33IkWd+4DfuYqdksIOLT/kfEzY5 S7G7G1sAVBpA== X-IronPort-AV: E=Sophos;i="5.77,287,1596524400"; d="scan'208";a="334538715" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.160]) by fmsmga004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Sep 2020 09:08:13 -0700 Date: Mon, 21 Sep 2020 09:08:12 -0700 From: Sean Christopherson To: Maxim Levitsky Cc: kvm@vger.kernel.org, Vitaly Kuznetsov , "H. Peter Anvin" , Joerg Roedel , Ingo Molnar , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Wanpeng Li , Borislav Petkov , Jim Mattson , linux-kernel@vger.kernel.org, Paolo Bonzini , Thomas Gleixner Subject: Re: [PATCH v5 2/4] KVM: x86: report negative values from wrmsr to userspace Message-ID: <20200921160812.GA23989@linux.intel.com> References: <20200921131923.120833-1-mlevitsk@redhat.com> <20200921131923.120833-3-mlevitsk@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200921131923.120833-3-mlevitsk@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 21, 2020 at 04:19:21PM +0300, Maxim Levitsky wrote: > This will allow us to make some MSR writes fatal to the guest > (e.g when out of memory condition occurs) > > Signed-off-by: Maxim Levitsky > --- > arch/x86/kvm/emulate.c | 7 +++++-- > arch/x86/kvm/x86.c | 5 +++-- > 2 files changed, 8 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index 1d450d7710d63..d855304f5a509 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -3702,13 +3702,16 @@ static int em_dr_write(struct x86_emulate_ctxt *ctxt) > static int em_wrmsr(struct x86_emulate_ctxt *ctxt) > { > u64 msr_data; > + int ret; > > msr_data = (u32)reg_read(ctxt, VCPU_REGS_RAX) > | ((u64)reg_read(ctxt, VCPU_REGS_RDX) << 32); > - if (ctxt->ops->set_msr(ctxt, reg_read(ctxt, VCPU_REGS_RCX), msr_data)) > + > + ret = ctxt->ops->set_msr(ctxt, reg_read(ctxt, VCPU_REGS_RCX), msr_data); > + if (ret > 0) > return emulate_gp(ctxt, 0); > > - return X86EMUL_CONTINUE; > + return ret < 0 ? X86EMUL_UNHANDLEABLE : X86EMUL_CONTINUE; > } > > static int em_rdmsr(struct x86_emulate_ctxt *ctxt) > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 063d70e736f7f..b6c67ab7c4f34 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -1612,15 +1612,16 @@ int kvm_emulate_wrmsr(struct kvm_vcpu *vcpu) > { > u32 ecx = kvm_rcx_read(vcpu); > u64 data = kvm_read_edx_eax(vcpu); > + int ret = kvm_set_msr(vcpu, ecx, data); > > - if (kvm_set_msr(vcpu, ecx, data)) { > + if (ret > 0) { > trace_kvm_msr_write_ex(ecx, data); > kvm_inject_gp(vcpu, 0); > return 1; > } > > trace_kvm_msr_write(ecx, data); Tracing the access as non-faulting feels wrong. The WRMSR has not completed, e.g. if userspace cleanly handles -ENOMEM and restarts the guest, KVM would trace the WRMSR twice. What about: int ret = kvm_set_msr(vcpu, ecx, data); if (ret < 0) return ret; if (ret) { trace_kvm_msr_write_ex(ecx, data); kvm_inject_gp(vcpu, 0); return 1; } trace_kvm_msr_write(ecx, data); return kvm_skip_emulated_instruction(vcpu); > - return kvm_skip_emulated_instruction(vcpu); > + return ret < 0 ? ret : kvm_skip_emulated_instruction(vcpu); > } > EXPORT_SYMBOL_GPL(kvm_emulate_wrmsr); > > -- > 2.26.2 >