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 434D0C433EF for ; Wed, 6 Apr 2022 05:20:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232690AbiDFFVK (ORCPT ); Wed, 6 Apr 2022 01:21:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35378 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1849509AbiDFCig (ORCPT ); Tue, 5 Apr 2022 22:38:36 -0400 Received: from mail-pg1-x52f.google.com (mail-pg1-x52f.google.com [IPv6:2607:f8b0:4864:20::52f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5FF99289FA2 for ; Tue, 5 Apr 2022 16:44:54 -0700 (PDT) Received: by mail-pg1-x52f.google.com with SMTP id s21so726470pgs.4 for ; Tue, 05 Apr 2022 16:44:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=qPGFyn3NlhtdM0CB2XMTbA0Uo1oxIfOYwzOJo7Agi4U=; b=LepKXMSWMmLTJMx/RVIVgA8Ej9I2cpV6nhMtHtbLF3ypiQIRCuglxwR1xPwT/OF2DU 2m1eHvrUvwtxfhySbsR2o2XcXy1BvnPsplzp7tiYgRWCfmwGmZJz7n3CfaJhxpZNfUzS 4eVAqxclqskG4diyD/E8CQCoPLcVWWMwsO3oKoLsPT8DiRnyUIZyREIun3Mm4wbi/QVq SeMU9ojc3ROCsGTdUyDwJgylaf9w/q0h1GWcLY1NKWAcAohNu3ZkyLxAudkN8Q4tHPNR tH32YHsuxImOHfKdewI6lY3cIWEhd74B5kAhfKdP/qD7rELab5GD7kpcHiW7lbsPp06t wrjA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=qPGFyn3NlhtdM0CB2XMTbA0Uo1oxIfOYwzOJo7Agi4U=; b=GPNRayQqTW6wjqnFDAkpzrJhLCHTl2Uk68s+7FPBTU/cAkBNGDGlpIivE10IJOTEHY hiNeWL+jmS5ZbF62c8t5yjewdz46E7MGb3cQHM/HpHQ8mli+lGsm/CVeD6n6WXziWpzE myy2zmQIHFS/yamd6kYDTPQtFE6WC5b0PtkomjsU0dsko/SDT5uY0Qh+n9f3ukvSz0KU ikkphreNsILcCcnUuyLsev4tjLtv6TIV8SZk4OjN8queSf0WcFMktkwtFBDqVaY1+hKA tbda6Lq8iLFWEopUm8Sb6Vc/mqpKSqd+jpu7UR/Y4MI5P2g4I+IxnWwoGhVtYfllN382 Y1+A== X-Gm-Message-State: AOAM5337lyDgqBRTAzXMe3Qk7mmgEOGntsTJnJfyzog4olfdmjNTpQBX CreeIu3TzIFj3icmYnn5D23jEj4llWHTHA== X-Google-Smtp-Source: ABdhPJySJ035zgZ6xzFWLjkm7h6F+Ek4V/GT1gQlZSLw6ceUS6ENxczqOl6xJXsVR//c/6Lk2GK7YQ== X-Received: by 2002:a05:6a00:b8e:b0:4fa:de88:9fc7 with SMTP id g14-20020a056a000b8e00b004fade889fc7mr5909203pfj.56.1649202293563; Tue, 05 Apr 2022 16:44:53 -0700 (PDT) Received: from google.com (157.214.185.35.bc.googleusercontent.com. [35.185.214.157]) by smtp.gmail.com with ESMTPSA id j7-20020a056a00130700b004b9f7cd94a4sm16741813pfu.56.2022.04.05.16.44.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Apr 2022 16:44:53 -0700 (PDT) Date: Tue, 5 Apr 2022 23:44:49 +0000 From: Sean Christopherson To: Chenyi Qiang Cc: Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Xiaoyao Li , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 1/3] KVM: X86: Save&restore the triple fault request Message-ID: References: <20220318074955.22428-1-chenyi.qiang@intel.com> <20220318074955.22428-2-chenyi.qiang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Apr 05, 2022, Sean Christopherson wrote: > On Fri, Mar 18, 2022, Chenyi Qiang wrote: > > @@ -4976,6 +4980,9 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu, > > } > > } > > > > + if (events->flags & KVM_VCPUEVENT_TRIPLE_FAULT) > > + kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu); > > + > > kvm_make_request(KVM_REQ_EVENT, vcpu); > > Looks correct, but this really needs a selftest, at least for the SET path since > the intent is to use that for the NOTIFY handling. Doesn't need to be super fancy, > e.g. do port I/O from L2, inject a triple fault, and verify L1 sees the appropriate > exit. > > Aha! And for the GET path, abuse KVM_X86_SET_MCE with CR4.MCE=0 to coerce KVM into > making a KVM_REQ_TRIPLE_FAULT, that way there's no need to try and hit a timing > window to intercept the request. Drat, I bet that MCE path means the WARN in nested_vmx_vmexit() can be triggered by userspace. If so, this patch makes it really, really easy to hit, e.g. queue the request while L2 is active, then do KVM_SET_NESTED_STATE to force an "exit" without bouncing through kvm_check_nested_events(). WARN_ON_ONCE(kvm_check_request(KVM_REQ_TRIPLE_FAULT, vcpu)) I don't think SVM has a user-triggerable WARN, but the request should still be dropped on forced exit from L2, e.g. I believe this is the correct fix: diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 9a6dc2b38fcf..18c5e96b12a5 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -1128,6 +1128,7 @@ void svm_leave_nested(struct kvm_vcpu *vcpu) if (is_guest_mode(vcpu)) { svm->nested.nested_run_pending = 0; svm->nested.vmcb12_gpa = INVALID_GPA; + kvm_clear_request(KVM_REQ_TRIPLE_FAULT, vcpu); leave_guest_mode(vcpu); diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index f18744f7ff82..0587ef647553 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -6276,6 +6276,7 @@ void vmx_leave_nested(struct kvm_vcpu *vcpu) { if (is_guest_mode(vcpu)) { to_vmx(vcpu)->nested.nested_run_pending = 0; + kvm_clear_request(KVM_REQ_TRIPLE_FAULT, vcpu); nested_vmx_vmexit(vcpu, -1, 0, 0); } free_nested(vcpu);