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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 05D39C64990 for ; Thu, 25 Aug 2022 14:16:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240650AbiHYOQ3 (ORCPT ); Thu, 25 Aug 2022 10:16:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57666 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235320AbiHYOQ1 (ORCPT ); Thu, 25 Aug 2022 10:16:27 -0400 Received: from vps-vb.mhejs.net (vps-vb.mhejs.net [37.28.154.113]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C495B9DFB9; Thu, 25 Aug 2022 07:16:24 -0700 (PDT) Received: from MUA by vps-vb.mhejs.net with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94.2) (envelope-from ) id 1oRDea-0002Pj-KL; Thu, 25 Aug 2022 16:16:16 +0200 Message-ID: Date: Thu, 25 Aug 2022 16:16:10 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Content-Language: en-US To: "Shukla, Santosh" Cc: Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Jim Mattson , Joerg Roedel , Tom Lendacky , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mlevitsk@redhat.com References: <20220810061226.1286-1-santosh.shukla@amd.com> <20220810061226.1286-6-santosh.shukla@amd.com> <1062bf85-0d44-011b-2377-d6be1485ce65@amd.com> <3752b74b-74e1-00fd-d80d-41104e07fe95@maciej.szmigiero.name> From: "Maciej S. Szmigiero" Subject: Re: [PATCHv3 5/8] KVM: SVM: Add VNMI support in inject_nmi In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 25.08.2022 16:05, Shukla, Santosh wrote: > On 8/25/2022 6:15 PM, Maciej S. Szmigiero wrote: >> On 25.08.2022 12:56, Shukla, Santosh wrote: >>> On 8/24/2022 6:26 PM, Maciej S. Szmigiero wrote: >>>> On 24.08.2022 14:13, Shukla, Santosh wrote: >>>>> Hi Maciej, >>>>> >>>>> On 8/11/2022 2:54 AM, Maciej S. Szmigiero wrote: >>>>>> On 10.08.2022 08:12, Santosh Shukla wrote: >>>>>>> Inject the NMI by setting V_NMI in the VMCB interrupt control. processor >>>>>>> will clear V_NMI to acknowledge processing has started and will keep the >>>>>>> V_NMI_MASK set until the processor is done with processing the NMI event. >>>>>>> >>>>>>> Signed-off-by: Santosh Shukla >>>>>>> --- >>>>>>> v3: >>>>>>> - Removed WARN_ON check. >>>>>>> >>>>>>> v2: >>>>>>> - Added WARN_ON check for vnmi pending. >>>>>>> - use `get_vnmi_vmcb` to get correct vmcb so to inject vnmi. >>>>>>> >>>>>>>     arch/x86/kvm/svm/svm.c | 7 +++++++ >>>>>>>     1 file changed, 7 insertions(+) >>>>>>> >>>>>>> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c >>>>>>> index e260e8cb0c81..8c4098b8a63e 100644 >>>>>>> --- a/arch/x86/kvm/svm/svm.c >>>>>>> +++ b/arch/x86/kvm/svm/svm.c >>>>>>> @@ -3479,7 +3479,14 @@ static void pre_svm_run(struct kvm_vcpu *vcpu) >>>>>>>     static void svm_inject_nmi(struct kvm_vcpu *vcpu) >>>>>>>     { >>>>>>>         struct vcpu_svm *svm = to_svm(vcpu); >>>>>>> +    struct vmcb *vmcb = NULL; >>>>>>>     +    if (is_vnmi_enabled(svm)) { >>>>>> >>>>>> I guess this should be "is_vnmi_enabled(svm) && !svm->nmi_l1_to_l2" >>>>>> since if nmi_l1_to_l2 is true then the NMI to be injected originally >>>>>> comes from L1's VMCB12 EVENTINJ field. >>>>>> >>>>> >>>>> Not sure if I understood the case fully.. so trying to sketch scenario here - >>>>> if nmi_l1_to_l2 is true then event is coming from EVTINJ. .which could >>>>> be one of following case - >>>>> 1) L0 (vnmi enabled) and L1 (vnmi disabled) >>>> >>>> As far as I can see in this case: >>>> is_vnmi_enabled() returns whether VMCB02's int_ctl has V_NMI_ENABLE bit set. >>>> >>> >>> For L1 with vnmi disabled case - is_vnmi_enabled()->get_vnmi_vmcb() will return false so the >>> execution path will opt EVTINJ model for re-injection. >> >> I guess by "get_vnmi_vmcb() will return false" you mean it will return NULL, >> since this function returns a pointer, not a bool. >> > > Yes, I meant is_vnmi_enabled() will return false if vnmi param is unset. > >> I can't see however, how this will happen: >>> static inline struct vmcb *get_vnmi_vmcb(struct vcpu_svm *svm) >>> { >>>     if (!vnmi) >>>         return NULL; >>         ^ "vnmi" variable controls whether L0 uses vNMI, >>        so this variable is true in our case >> > > No. > > In L1 case (vnmi disabled) - vnmi param will be false. Perhaps there was a misunderstanding here - the case here isn't the code under discussion running as L1, but as L0 where L1 not using vNMI - L1 here can be an old version of KVM, or Hyper-V, or any other hypervisor. In this case L0 is re-injecting an EVENTINJ NMI into L2 on the behalf of L1. That's when "nmi_l1_to_l2" is true. Since the code is physically running on L0 (which makes use of vNMI) it has the "vnmi" param set. So is_vnmi_enabled() will return true and vNMI will be used for the re-injection instead of the required EVENTINJ. > In L0 case (vnmi enabled) - vnmi param will be true. > > So in L1 case, is_vnmi_enabled() will return false and > in L0 case will return true. > > Thanks, > Santosh Thanks, Maciej