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=-8.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, HK_RANDOM_FROM,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 D649FC10DCE for ; Sun, 15 Mar 2020 05:23:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B71B420722 for ; Sun, 15 Mar 2020 05:23:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727729AbgCOFXP (ORCPT ); Sun, 15 Mar 2020 01:23:15 -0400 Received: from mga18.intel.com ([134.134.136.126]:47872 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727605AbgCOFXO (ORCPT ); Sun, 15 Mar 2020 01:23:14 -0400 IronPort-SDR: FFEoVqgTKixI/hiiJPvpFDJj7QPMAfOjPtvpxnhlhOYiHtmUcZ6VoI17oD/nPfU2mYVN9bjf6Y zTRNqRHGK1Lw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Mar 2020 22:23:13 -0700 IronPort-SDR: Yf1BOkPfQGdz2UqcGKfCPiNK6LvrRNiv7kz7GpxeFD7Pc+JWoVlkQGSrwCggXBNz3/54ff9l3x Xx4aLklElGbA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,555,1574150400"; d="scan'208";a="267194261" Received: from lxy-clx-4s.sh.intel.com ([10.239.43.160]) by fmsmga004.fm.intel.com with ESMTP; 14 Mar 2020 22:23:10 -0700 From: Xiaoyao Li To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , hpa@zytor.com, Paolo Bonzini , Sean Christopherson , kvm@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org Cc: Andy Lutomirski , Peter Zijlstra , Arvind Sankar , Fenghua Yu , Tony Luck , Vitaly Kuznetsov , Jim Mattson , Xiaoyao Li Subject: [PATCH v5 6/9] kvm: vmx: Extend VMX's #AC interceptor to handle split lock #AC happens in guest Date: Sun, 15 Mar 2020 13:05:14 +0800 Message-Id: <20200315050517.127446-7-xiaoyao.li@intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200315050517.127446-1-xiaoyao.li@intel.com> References: <20200315050517.127446-1-xiaoyao.li@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There are two types of #AC can be generated in Intel CPUs: 1. legacy alignment check #AC; 2. split lock #AC; Legacy alignment check #AC can be injected to guest if guest has enabled alignemnet check. when host enables split lock detectin, i.e., sld_warn or sld_fatal, there will be an unexpected #AC in guest and intercepted by KVM because KVM doesn't virtualize this feature to guest and hardware value of MSR_TEST_CTRL.SLD bit stays unchanged when vcpu is running. To handle this unexpected #AC, treat guest just like host usermode that calling handle_user_split_lock(): - If host is sld_warn, it warns and set TIF_SLD so that __switch_to_xtra() does the MSR_TEST_CTRL.SLD bit switching when control transfer to/from this vcpu. - If host is sld_fatal, forward #AC to userspace, the similar as sending SIGBUS. Suggested-by: Sean Christopherson Signed-off-by: Xiaoyao Li --- arch/x86/kvm/vmx/vmx.c | 30 +++++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 40b1e6138cd5..3fb132ad489d 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -4609,6 +4609,12 @@ static int handle_machine_check(struct kvm_vcpu *vcpu) return 1; } +static inline bool guest_cpu_alignment_check_enabled(struct kvm_vcpu *vcpu) +{ + return vmx_get_cpl(vcpu) == 3 && kvm_read_cr0_bits(vcpu, X86_CR0_AM) && + (kvm_get_rflags(vcpu) & X86_EFLAGS_AC); +} + static int handle_exception_nmi(struct kvm_vcpu *vcpu) { struct vcpu_vmx *vmx = to_vmx(vcpu); @@ -4674,9 +4680,6 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu) return handle_rmode_exception(vcpu, ex_no, error_code); switch (ex_no) { - case AC_VECTOR: - kvm_queue_exception_e(vcpu, AC_VECTOR, error_code); - return 1; case DB_VECTOR: dr6 = vmcs_readl(EXIT_QUALIFICATION); if (!(vcpu->guest_debug & @@ -4705,6 +4708,27 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu) kvm_run->debug.arch.pc = vmcs_readl(GUEST_CS_BASE) + rip; kvm_run->debug.arch.exception = ex_no; break; + case AC_VECTOR: + /* + * Reflect #AC to the guest if it's expecting the #AC, i.e. has + * legacy alignment check enabled. Pre-check host split lock + * support to avoid the VMREADs needed to check legacy #AC, + * i.e. reflect the #AC if the only possible source is legacy + * alignment checks. + */ + if (!split_lock_detect_on() || + guest_cpu_alignment_check_enabled(vcpu)) { + kvm_queue_exception_e(vcpu, AC_VECTOR, error_code); + return 1; + } + + /* + * Forward the #AC to userspace if kernel policy does not allow + * temporarily disabling split lock detection. + */ + if (handle_user_split_lock(kvm_rip_read(vcpu))) + return 1; + fallthrough; default: kvm_run->exit_reason = KVM_EXIT_EXCEPTION; kvm_run->ex.exception = ex_no; -- 2.20.1