From patchwork Tue Mar 24 15:18:56 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Xiaoyao Li X-Patchwork-Id: 11455797 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id BB92F6CA for ; Tue, 24 Mar 2020 15:37:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A6A8D208DB for ; Tue, 24 Mar 2020 15:37:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728627AbgCXPh2 (ORCPT ); Tue, 24 Mar 2020 11:37:28 -0400 Received: from mga05.intel.com ([192.55.52.43]:40198 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728608AbgCXPh1 (ORCPT ); Tue, 24 Mar 2020 11:37:27 -0400 IronPort-SDR: ZG4pQCHbgfmCrF8/DezJ0ChUisQ1FILqliWZCDt8fG1JBWqEhbaOtm7op5sN6iuLFY0qB0oSpb 8LKeEPk4WzgA== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Mar 2020 08:37:26 -0700 IronPort-SDR: Icj05jCEMrNmV0/gz7KTNVEHCBHp5zk00/klmMqsmSqXPLcnqIK/EPSSgJBhksLqJlDNY1UsNN AeEYK/RHDxSA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,300,1580803200"; d="scan'208";a="393319737" Received: from lxy-clx-4s.sh.intel.com ([10.239.43.39]) by orsmga004.jf.intel.com with ESMTP; 24 Mar 2020 08:37:22 -0700 From: Xiaoyao Li To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , hpa@zytor.com, Paolo Bonzini , Sean Christopherson Cc: x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Andy Lutomirski , Peter Zijlstra , Arvind Sankar , Fenghua Yu , Tony Luck , Xiaoyao Li Subject: [PATCH v6 5/8] kvm: vmx: Extend VMX's #AC interceptor to handle split lock #AC happens in guest Date: Tue, 24 Mar 2020 23:18:56 +0800 Message-Id: <20200324151859.31068-6-xiaoyao.li@intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200324151859.31068-1-xiaoyao.li@intel.com> References: <20200324151859.31068-1-xiaoyao.li@intel.com> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@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 094dbe375f01..300e1e149372 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -4613,6 +4613,12 @@ 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); @@ -4678,9 +4684,6 @@ 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 & @@ -4709,6 +4712,27 @@ 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;