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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 A3B6AC433DB for ; Wed, 27 Jan 2021 04:57:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7A3D72064A for ; Wed, 27 Jan 2021 04:57:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238586AbhA0E0G (ORCPT ); Tue, 26 Jan 2021 23:26:06 -0500 Received: from mga05.intel.com ([192.55.52.43]:24395 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726043AbhA0Bt3 (ORCPT ); Tue, 26 Jan 2021 20:49:29 -0500 IronPort-SDR: J0RjPeR94lEuMxR607VON9VktjuiEZlEldtLEcbc4XtZTwSu7ReZB6zF3c9tKHIXEL1iEeEd1N yYPzTCtCDNWA== X-IronPort-AV: E=McAfee;i="6000,8403,9876"; a="264824538" X-IronPort-AV: E=Sophos;i="5.79,378,1602572400"; d="scan'208";a="264824538" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jan 2021 17:48:43 -0800 IronPort-SDR: 9tuN3Fp+CybG/N9oZJtI7xtW4bd61dwTVO1z/ptvFtbasiC0wFjdNoWyUFpmWca0QmEbIwpvec aJYfOOt6AUnQ== X-IronPort-AV: E=Sophos;i="5.79,378,1602572400"; d="scan'208";a="388095597" Received: from cqiang-mobl.ccr.corp.intel.com (HELO [10.238.1.32]) ([10.238.1.32]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jan 2021 17:48:41 -0800 Subject: Re: [RESEND PATCH 1/2] KVM: X86: Add support for the emulation of DR6_BUS_LOCK bit To: Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Xiaoyao Li Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210108064924.1677-1-chenyi.qiang@intel.com> <20210108064924.1677-2-chenyi.qiang@intel.com> From: Chenyi Qiang Message-ID: <5e81257e-df94-271e-3aef-cab54682174e@intel.com> Date: Wed, 27 Jan 2021 09:48:38 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 1/27/2021 12:31 AM, Paolo Bonzini wrote: > On 08/01/21 07:49, Chenyi Qiang wrote: >> To avoid breaking the CPUs without bus lock detection, activate the >> DR6_BUS_LOCK bit (bit 11) conditionally in DR6_FIXED_1 bits. >> >> The set/clear of DR6_BUS_LOCK is similar to the DR6_RTM in DR6 >> register. The processor clears DR6_BUS_LOCK when bus lock debug >> exception is generated. (For all other #DB the processor sets this bit >> to 1.) Software #DB handler should set this bit before returning to the >> interrupted task. >> >> For VM exit caused by debug exception, bit 11 of the exit qualification >> is set to indicate that a bus lock debug exception condition was >> detected. The VMM should emulate the exception by clearing bit 11 of the >> guest DR6. > > Please rename DR6_INIT to DR6_ACTIVE_LOW, and then a lot of changes > become simpler: > >> -        dr6 |= DR6_BD | DR6_RTM; >> +        dr6 |= DR6_BD | DR6_RTM | DR6_BUS_LOCK; > > dr6 |= DR6_BD | DR6_ACTIVE_LOW; > >>           ctxt->ops->set_dr(ctxt, 6, dr6); >>           return emulate_db(ctxt); >>       } >> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c >> index cce0143a6f80..3d8a0e30314f 100644 >> --- a/arch/x86/kvm/svm/svm.c >> +++ b/arch/x86/kvm/svm/svm.c >> @@ -1860,7 +1860,7 @@ static void svm_sync_dirty_debug_regs(struct >> kvm_vcpu *vcpu) >>       get_debugreg(vcpu->arch.db[2], 2); >>       get_debugreg(vcpu->arch.db[3], 3); >>       /* >> -     * We cannot reset svm->vmcb->save.dr6 to DR6_FIXED_1|DR6_RTM here, >> +     * We cannot reset svm->vmcb->save.dr6 to >> DR6_FIXED_1|DR6_RTM|DR6_BUS_LOCK here, > > We cannot reset svm->vmcb->save.dr6 to DR6_ACTIVE_LOW > >>        * because db_interception might need it.  We can do it before >> vmentry. >>        */ >>       vcpu->arch.dr6 = svm->vmcb->save.dr6; >> @@ -1911,7 +1911,7 @@ static int db_interception(struct vcpu_svm *svm) >>       if (!(svm->vcpu.guest_debug & >>             (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP)) && >>           !svm->nmi_singlestep) { >> -        u32 payload = (svm->vmcb->save.dr6 ^ DR6_RTM) & ~DR6_FIXED_1; >> +        u32 payload = (svm->vmcb->save.dr6 ^ (DR6_RTM|DR6_BUS_LOCK)) >> & ~DR6_FIXED_1; > > u32 payload = svm->vmcb->save.dr6 ^ DR6_ACTIVE_LOW; > >>           kvm_queue_exception_p(&svm->vcpu, DB_VECTOR, payload); >>           return 1; >>       } >> @@ -3778,7 +3778,7 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct >> kvm_vcpu *vcpu) >>       if (unlikely(svm->vcpu.arch.switch_db_regs & >> KVM_DEBUGREG_WONT_EXIT)) >>           svm_set_dr6(svm, vcpu->arch.dr6); >>       else >> -        svm_set_dr6(svm, DR6_FIXED_1 | DR6_RTM); >> +        svm_set_dr6(svm, DR6_FIXED_1 | DR6_RTM | DR6_BUS_LOCK); > > svm_set_dr6(svm, DR6_ACTIVE_LOW); > >>       clgi(); >>       kvm_load_guest_xsave_state(vcpu); >> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c >> index e2f26564a12d..c5d71a9b3729 100644 >> --- a/arch/x86/kvm/vmx/nested.c >> +++ b/arch/x86/kvm/vmx/nested.c >> @@ -412,7 +412,7 @@ static int nested_vmx_check_exception(struct >> kvm_vcpu *vcpu, unsigned long *exit >>               if (!has_payload) { >>                   payload = vcpu->arch.dr6; >>                   payload &= ~(DR6_FIXED_1 | DR6_BT); >> -                payload ^= DR6_RTM; >> +                payload ^= DR6_RTM | DR6_BUS_LOCK; > > payload &= ~DR6_BT; > payload ^= DR6_ACTIVE_LOW; > >>               } >>               *exit_qual = payload; >>           } else >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index 3f7c1fc7a3ce..06de2b9e57f3 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -483,19 +483,20 @@ void kvm_deliver_exception_payload(struct >> kvm_vcpu *vcpu) >>            */ >>           vcpu->arch.dr6 &= ~DR_TRAP_BITS; >>           /* >> -         * DR6.RTM is set by all #DB exceptions that don't clear it. >> +         * DR6.RTM and DR6.BUS_LOCK are set by all #DB exceptions >> +         * that don't clear it. >>            */ >> -        vcpu->arch.dr6 |= DR6_RTM; >> +        vcpu->arch.dr6 |= DR6_RTM | DR6_BUS_LOCK; >>           vcpu->arch.dr6 |= payload; >>           /* >> -         * Bit 16 should be set in the payload whenever the #DB >> -         * exception should clear DR6.RTM. This makes the payload >> -         * compatible with the pending debug exceptions under VMX. >> -         * Though not currently documented in the SDM, this also >> -         * makes the payload compatible with the exit qualification >> -         * for #DB exceptions under VMX. >> +         * Bit 16/Bit 11 should be set in the payload whenever >> +         * the #DB exception should clear DR6.RTM/DR6.BUS_LOCK. >> +         * This makes the payload compatible with the pending debug >> +         * exceptions under VMX. Though not currently documented in >> +         * the SDM, this also makes the payload compatible with the >> +         * exit qualification for #DB exceptions under VMX. >>            */ >> -        vcpu->arch.dr6 ^= payload & DR6_RTM; >> +        vcpu->arch.dr6 ^= payload & (DR6_RTM | DR6_BUS_LOCK); > > vcpu->arch.dr6 &= ~DR_TRAP_BITS; > vcpu->arch.dr6 |= DR6_ACTIVE_LOW; > vcpu->arch.dr6 |= payload; > vcpu->arch.dr6 ^= payload & DR6_ACTIVE_LOW; > > (with comments :)) > > and so on. > > Thanks! > > Paolo > Will do the changes. Thanks! Chenyi >>           /* >>            * The #DB payload is defined as compatible with the 'pending >> @@ -1126,6 +1127,9 @@ static u64 kvm_dr6_fixed(struct kvm_vcpu *vcpu) >>       if (!guest_cpuid_has(vcpu, X86_FEATURE_RTM)) >>           fixed |= DR6_RTM; >> + >> +    if (!guest_cpuid_has(vcpu, X86_FEATURE_BUS_LOCK_DETECT)) >> +        fixed |= DR6_BUS_LOCK; >>       return fixed; >>   } >> @@ -7197,7 +7201,8 @@ static int kvm_vcpu_do_singlestep(struct >> kvm_vcpu *vcpu) >>       struct kvm_run *kvm_run = vcpu->run; >>       if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { >> -        kvm_run->debug.arch.dr6 = DR6_BS | DR6_FIXED_1 | DR6_RTM; >> +        kvm_run->debug.arch.dr6 = DR6_BS | DR6_FIXED_1 | DR6_RTM | >> +                      DR6_BUS_LOCK; >>           kvm_run->debug.arch.pc = kvm_get_linear_rip(vcpu); >>           kvm_run->debug.arch.exception = DB_VECTOR; >>           kvm_run->exit_reason = KVM_EXIT_DEBUG; >> @@ -7241,7 +7246,8 @@ static bool kvm_vcpu_check_breakpoint(struct >> kvm_vcpu *vcpu, int *r) >>                          vcpu->arch.eff_db); >>           if (dr6 != 0) { >> -            kvm_run->debug.arch.dr6 = dr6 | DR6_FIXED_1 | DR6_RTM; >> +            kvm_run->debug.arch.dr6 = dr6 | DR6_FIXED_1 | DR6_RTM | >> +                          DR6_BUS_LOCK; >>               kvm_run->debug.arch.pc = eip; >>               kvm_run->debug.arch.exception = DB_VECTOR; >>               kvm_run->exit_reason = KVM_EXIT_DEBUG; >> >