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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, 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 C6C7BC4332E for ; Thu, 19 Mar 2020 18:56:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9B3CE2070A for ; Thu, 19 Mar 2020 18:56:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="DYwwCnRB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727286AbgCSS4S (ORCPT ); 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Thu, 19 Mar 2020 18:56:14 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 02JInoxl139237; Thu, 19 Mar 2020 18:56:14 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserp3020.oracle.com with ESMTP id 2ys92mxsca-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 19 Mar 2020 18:56:13 +0000 Received: from abhmp0016.oracle.com (abhmp0016.oracle.com [141.146.116.22]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 02JIuCfi014085; Thu, 19 Mar 2020 18:56:12 GMT Received: from localhost.localdomain (/10.65.178.104) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 19 Mar 2020 11:56:12 -0700 Subject: Re: [PATCH] KVM: nSVM: check for EFER.SVME=1 before entering guest To: Paolo Bonzini , linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <1584535300-6571-1-git-send-email-pbonzini@redhat.com> <6426c98d-d206-aeb7-93fa-da62b77df21a@redhat.com> From: Krish Sadhukhan Message-ID: <3ce6d879-5e53-cdf1-a876-542044511836@oracle.com> Date: Thu, 19 Mar 2020 11:56:02 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <6426c98d-d206-aeb7-93fa-da62b77df21a@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9565 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 mlxlogscore=999 mlxscore=0 spamscore=0 bulkscore=0 adultscore=0 suspectscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003190078 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9565 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 impostorscore=0 mlxlogscore=999 mlxscore=0 phishscore=0 adultscore=0 suspectscore=0 clxscore=1015 priorityscore=1501 lowpriorityscore=0 bulkscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003190078 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/19/20 3:05 AM, Paolo Bonzini wrote: > On 18/03/20 19:40, Krish Sadhukhan wrote: >> On 3/18/20 5:41 AM, Paolo Bonzini wrote: >>> EFER is set for L2 using svm_set_efer, which hardcodes EFER_SVME to 1 >>> and hides >>> an incorrect value for EFER.SVME in the L1 VMCB.  Perform the check >>> manually >>> to detect invalid guest state. >>> >>> Reported-by: Krish Sadhukhan >>> Signed-off-by: Paolo Bonzini >>> --- >>>   arch/x86/kvm/svm.c | 3 +++ >>>   1 file changed, 3 insertions(+) >>> >>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c >>> index 08568ae9f7a1..2125c6ae5951 100644 >>> --- a/arch/x86/kvm/svm.c >>> +++ b/arch/x86/kvm/svm.c >>> @@ -3558,6 +3558,9 @@ static bool nested_svm_vmrun_msrpm(struct >>> vcpu_svm *svm) >>>     static bool nested_vmcb_checks(struct vmcb *vmcb) >>>   { >>> +    if ((vmcb->save.efer & EFER_SVME) == 0) >>> +        return false; >>> + >>>       if ((vmcb->control.intercept & (1ULL << INTERCEPT_VMRUN)) == 0) >>>           return false; >>> >> Ah! This now tells me that I forgot the KVM fix that was supposed to >> accompany my patchset. > Heh, indeed. I was puzzled for a second after applying it, then decided > I would just fix it myself. :) > >> Do we need this check in software ? I wasn't checking the bit in KVM and >> instead I was just making sure that L0 sets that bit based on the >> setting in nested vmcb: Thanks ! > The only effect of the function below over svm_set_efer is to guarantee > a vmrun error to happen. Doing the test in nested_vmcb_checks is more > consistent with other must-be-one bits such as the VMRUN intercept, and > it's also a smaller patch. Reviewed-by: Krish Sadhukhan > > Paolo > >> +static void nested_svm_set_efer(struct kvm_vcpu *vcpu, u64 >> nested_vmcb_efer) >> +{ >> +       svm_set_efer(vcpu, nested_vmcb_efer); >> + >> +       if (!(nested_vmcb_efer & EFER_SVME)) >> +               to_svm(vcpu)->vmcb->save.efer &= ~EFER_SVME; >> +} >> + >>  static int is_external_interrupt(u32 info) >>  { >>         info &= SVM_EVTINJ_TYPE_MASK | SVM_EVTINJ_VALID; >> @@ -3554,7 +3562,7 @@ static void enter_svm_guest_mode(struct vcpu_svm >> *svm, u64 >>         svm->vmcb->save.gdtr = nested_vmcb->save.gdtr; >>         svm->vmcb->save.idtr = nested_vmcb->save.idtr; >>         kvm_set_rflags(&svm->vcpu, nested_vmcb->save.rflags); >> -       svm_set_efer(&svm->vcpu, nested_vmcb->save.efer); >> +       nested_svm_set_efer(&svm->vcpu, nested_vmcb->save.efer); >>         svm_set_cr0(&svm->vcpu, nested_vmcb->save.cr0); >>         svm_set_cr4(&svm->vcpu, nested_vmcb->save.cr4); >>         if (npt_enabled) { >>