From patchwork Thu Nov 25 00:20:01 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Isaku Yamahata X-Patchwork-Id: 12638163 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 3AE4CC433FE for ; Thu, 25 Nov 2021 00:21:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352897AbhKYAYl (ORCPT ); Wed, 24 Nov 2021 19:24:41 -0500 Received: from mga14.intel.com ([192.55.52.115]:6408 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352787AbhKYAYT (ORCPT ); Wed, 24 Nov 2021 19:24:19 -0500 X-IronPort-AV: E=McAfee;i="6200,9189,10178"; a="235649680" X-IronPort-AV: E=Sophos;i="5.87,261,1631602800"; d="scan'208";a="235649680" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Nov 2021 16:21:08 -0800 X-IronPort-AV: E=Sophos;i="5.87,261,1631602800"; d="scan'208";a="675042159" Received: from ls.sc.intel.com (HELO localhost) ([143.183.96.54]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Nov 2021 16:21:08 -0800 From: isaku.yamahata@intel.com To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , erdemaktas@google.com, Connor Kuehl , Sean Christopherson , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: isaku.yamahata@intel.com, isaku.yamahata@gmail.com, Sean Christopherson , Kai Huang Subject: [RFC PATCH v3 18/59] KVM: x86: Add flag to mark TSC as immutable (for TDX) Date: Wed, 24 Nov 2021 16:20:01 -0800 Message-Id: <00772535f09b2bf98e6bc7008e81c6ffb381ed84.1637799475.git.isaku.yamahata@intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Sean Christopherson The TSC for TDX1 guests is fixed at TD creation time. Add tsc_immutable to reflect that the TSC of the guest cannot be changed in any way, and use it to short circuit all paths that lead to one of the myriad TSC adjustment flows. Suggested-by: Kai Huang Signed-off-by: Sean Christopherson Signed-off-by: Isaku Yamahata --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/x86.c | 35 +++++++++++++++++++++++++-------- 2 files changed, 28 insertions(+), 8 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index e912e1e853ef..f3808672c720 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1122,6 +1122,7 @@ struct kvm_arch { int audit_point; #endif + bool tsc_immutable; bool backwards_tsc_observed; bool boot_vcpu_runs_old_kvmclock; u32 bsp_vcpu_id; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index fefa4602e879..0ebd60846079 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2247,7 +2247,9 @@ static int set_tsc_khz(struct kvm_vcpu *vcpu, u32 user_tsc_khz, bool scale) u64 ratio; /* Guest TSC same frequency as host TSC? */ - if (!scale) { + if (!scale || vcpu->kvm->arch.tsc_immutable) { + if (scale) + pr_warn_ratelimited("Guest TSC immutable, scaling not supported\n"); kvm_vcpu_write_tsc_multiplier(vcpu, kvm_default_tsc_scaling_ratio); return 0; } @@ -2534,6 +2536,9 @@ static void kvm_synchronize_tsc(struct kvm_vcpu *vcpu, u64 data) bool matched = false; bool synchronizing = false; + if (WARN_ON_ONCE(vcpu->kvm->arch.tsc_immutable)) + return; + raw_spin_lock_irqsave(&kvm->arch.tsc_write_lock, flags); offset = kvm_compute_l1_tsc_offset(vcpu, data); ns = get_kvmclock_base_ns(); @@ -2960,6 +2965,10 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) u8 pvclock_flags; bool use_master_clock; + /* Unable to update guest time if the TSC is immutable. */ + if (ka->tsc_immutable) + return 0; + kernel_ns = 0; host_tsc = 0; @@ -4372,7 +4381,8 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) if (tsc_delta < 0) mark_tsc_unstable("KVM discovered backwards TSC"); - if (kvm_check_tsc_unstable()) { + if (kvm_check_tsc_unstable() && + !vcpu->kvm->arch.tsc_immutable) { u64 offset = kvm_compute_l1_tsc_offset(vcpu, vcpu->arch.last_guest_tsc); kvm_vcpu_write_tsc_offset(vcpu, offset); @@ -4386,7 +4396,8 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) * On a host with synchronized TSC, there is no need to update * kvmclock on vcpu->cpu migration */ - if (!vcpu->kvm->arch.use_master_clock || vcpu->cpu == -1) + if ((!vcpu->kvm->arch.use_master_clock || vcpu->cpu == -1) && + !vcpu->kvm->arch.tsc_immutable) kvm_make_request(KVM_REQ_GLOBAL_CLOCK_UPDATE, vcpu); if (vcpu->cpu != cpu) kvm_make_request(KVM_REQ_MIGRATE_TIMER, vcpu); @@ -5352,10 +5363,11 @@ long kvm_arch_vcpu_ioctl(struct file *filp, break; } case KVM_SET_TSC_KHZ: { - u32 user_tsc_khz; + u32 user_tsc_khz = (u32)arg; r = -EINVAL; - user_tsc_khz = (u32)arg; + if (vcpu->kvm->arch.tsc_immutable) + goto out; if (kvm_has_tsc_control && user_tsc_khz >= kvm_max_guest_tsc_khz) @@ -10994,9 +11006,12 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu) if (mutex_lock_killable(&vcpu->mutex)) return; - vcpu_load(vcpu); - kvm_synchronize_tsc(vcpu, 0); - vcpu_put(vcpu); + + if (!kvm->arch.tsc_immutable) { + vcpu_load(vcpu); + kvm_synchronize_tsc(vcpu, 0); + vcpu_put(vcpu); + } /* poll control enabled by default */ vcpu->arch.msr_kvm_poll_control = 1; @@ -11253,6 +11268,10 @@ int kvm_arch_hardware_enable(void) if (backwards_tsc) { u64 delta_cyc = max_tsc - local_tsc; list_for_each_entry(kvm, &vm_list, vm_list) { + if (vcpu->kvm->arch.tsc_immutable) { + pr_warn_ratelimited("Backwards TSC observed and guest with immutable TSC active\n"); + continue; + } kvm->arch.backwards_tsc_observed = true; kvm_for_each_vcpu(i, vcpu, kvm) { vcpu->arch.tsc_offset_adjustment += delta_cyc;