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 B0855C433EF for ; Mon, 13 Jun 2022 14:07:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1380987AbiFMOHi (ORCPT ); Mon, 13 Jun 2022 10:07:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43210 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1381022AbiFMODZ (ORCPT ); Mon, 13 Jun 2022 10:03:25 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6E70E4550C; Mon, 13 Jun 2022 04:38:31 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id E7F56B80ECD; Mon, 13 Jun 2022 11:38:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 65DCCC34114; Mon, 13 Jun 2022 11:38:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655120308; bh=gbB36lepBkbWC774q08+PNylmooVNJXDF/maPQEkFZA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QPex+6N7BkGrKLLiGsHbn1k3BS/eVRjaFE2bw9SP4hEJzurBGHfm+RGIys++RjsME jjRVA5jU9MSqoQOvfuxy1RxSACbWTQavzTeICYUgLNPPjIfJdSuylpvxdWkpBY3vCP yt3cqko0EwtbOc8ZR245s5G1BdscW8dkq+13RN/g= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Maxim Levitsky , Paolo Bonzini Subject: [PATCH 5.18 306/339] KVM: SVM: fix tsc scaling cache logic Date: Mon, 13 Jun 2022 12:12:11 +0200 Message-Id: <20220613094936.039355710@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220613094926.497929857@linuxfoundation.org> References: <20220613094926.497929857@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Maxim Levitsky commit 11d39e8cc43e1c6737af19ca9372e590061b5ad2 upstream. SVM uses a per-cpu variable to cache the current value of the tsc scaling multiplier msr on each cpu. Commit 1ab9287add5e2 ("KVM: X86: Add vendor callbacks for writing the TSC multiplier") broke this caching logic. Refactor the code so that all TSC scaling multiplier writes go through a single function which checks and updates the cache. This fixes the following scenario: 1. A CPU runs a guest with some tsc scaling ratio. 2. New guest with different tsc scaling ratio starts on this CPU and terminates almost immediately. This ensures that the short running guest had set the tsc scaling ratio just once when it was set via KVM_SET_TSC_KHZ. Due to the bug, the per-cpu cache is not updated. 3. The original guest continues to run, it doesn't restore the msr value back to its own value, because the cache matches, and thus continues to run with a wrong tsc scaling ratio. Fixes: 1ab9287add5e2 ("KVM: X86: Add vendor callbacks for writing the TSC multiplier") Signed-off-by: Maxim Levitsky Message-Id: <20220606181149.103072-1-mlevitsk@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/svm/nested.c | 4 ++-- arch/x86/kvm/svm/svm.c | 32 ++++++++++++++++++++------------ arch/x86/kvm/svm/svm.h | 2 +- 3 files changed, 23 insertions(+), 15 deletions(-) --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -896,7 +896,7 @@ int nested_svm_vmexit(struct vcpu_svm *s if (svm->tsc_ratio_msr != kvm_default_tsc_scaling_ratio) { WARN_ON(!svm->tsc_scaling_enabled); vcpu->arch.tsc_scaling_ratio = vcpu->arch.l1_tsc_scaling_ratio; - svm_write_tsc_multiplier(vcpu, vcpu->arch.tsc_scaling_ratio); + __svm_write_tsc_multiplier(vcpu->arch.tsc_scaling_ratio); } svm->nested.ctl.nested_cr3 = 0; @@ -1293,7 +1293,7 @@ void nested_svm_update_tsc_ratio_msr(str vcpu->arch.tsc_scaling_ratio = kvm_calc_nested_tsc_multiplier(vcpu->arch.l1_tsc_scaling_ratio, svm->tsc_ratio_msr); - svm_write_tsc_multiplier(vcpu, vcpu->arch.tsc_scaling_ratio); + __svm_write_tsc_multiplier(vcpu->arch.tsc_scaling_ratio); } /* Inverse operation of nested_copy_vmcb_control_to_cache(). asid is copied too. */ --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -463,11 +463,24 @@ static int has_svm(void) return 1; } +void __svm_write_tsc_multiplier(u64 multiplier) +{ + preempt_disable(); + + if (multiplier == __this_cpu_read(current_tsc_ratio)) + goto out; + + wrmsrl(MSR_AMD64_TSC_RATIO, multiplier); + __this_cpu_write(current_tsc_ratio, multiplier); +out: + preempt_enable(); +} + static void svm_hardware_disable(void) { /* Make sure we clean up behind us */ if (tsc_scaling) - wrmsrl(MSR_AMD64_TSC_RATIO, SVM_TSC_RATIO_DEFAULT); + __svm_write_tsc_multiplier(SVM_TSC_RATIO_DEFAULT); cpu_svm_disable(); @@ -513,8 +526,7 @@ static int svm_hardware_enable(void) * Set the default value, even if we don't use TSC scaling * to avoid having stale value in the msr */ - wrmsrl(MSR_AMD64_TSC_RATIO, SVM_TSC_RATIO_DEFAULT); - __this_cpu_write(current_tsc_ratio, SVM_TSC_RATIO_DEFAULT); + __svm_write_tsc_multiplier(SVM_TSC_RATIO_DEFAULT); } @@ -915,11 +927,12 @@ static void svm_write_tsc_offset(struct vmcb_mark_dirty(svm->vmcb, VMCB_INTERCEPTS); } -void svm_write_tsc_multiplier(struct kvm_vcpu *vcpu, u64 multiplier) +static void svm_write_tsc_multiplier(struct kvm_vcpu *vcpu, u64 multiplier) { - wrmsrl(MSR_AMD64_TSC_RATIO, multiplier); + __svm_write_tsc_multiplier(multiplier); } + /* Evaluate instruction intercepts that depend on guest CPUID features. */ static void svm_recalc_instruction_intercepts(struct kvm_vcpu *vcpu, struct vcpu_svm *svm) @@ -1276,13 +1289,8 @@ static void svm_prepare_switch_to_guest( sev_es_prepare_switch_to_guest(hostsa); } - if (tsc_scaling) { - u64 tsc_ratio = vcpu->arch.tsc_scaling_ratio; - if (tsc_ratio != __this_cpu_read(current_tsc_ratio)) { - __this_cpu_write(current_tsc_ratio, tsc_ratio); - wrmsrl(MSR_AMD64_TSC_RATIO, tsc_ratio); - } - } + if (tsc_scaling) + __svm_write_tsc_multiplier(vcpu->arch.tsc_scaling_ratio); if (likely(tsc_aux_uret_slot >= 0)) kvm_set_user_return_msr(tsc_aux_uret_slot, svm->tsc_aux, -1ull); --- a/arch/x86/kvm/svm/svm.h +++ b/arch/x86/kvm/svm/svm.h @@ -558,7 +558,7 @@ int nested_svm_check_exception(struct vc bool has_error_code, u32 error_code); int nested_svm_exit_special(struct vcpu_svm *svm); void nested_svm_update_tsc_ratio_msr(struct kvm_vcpu *vcpu); -void svm_write_tsc_multiplier(struct kvm_vcpu *vcpu, u64 multiplier); +void __svm_write_tsc_multiplier(u64 multiplier); void nested_copy_vmcb_control_to_cache(struct vcpu_svm *svm, struct vmcb_control_area *control); void nested_copy_vmcb_save_to_cache(struct vcpu_svm *svm,