From patchwork Fri Apr 23 22:34:04 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 12221943 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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 3099DC433B4 for ; Fri, 23 Apr 2021 22:34:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 066246141C for ; Fri, 23 Apr 2021 22:34:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244176AbhDWWfS (ORCPT ); Fri, 23 Apr 2021 18:35:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36238 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244060AbhDWWe6 (ORCPT ); Fri, 23 Apr 2021 18:34:58 -0400 Received: from mail-qk1-x74a.google.com (mail-qk1-x74a.google.com [IPv6:2607:f8b0:4864:20::74a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17841C061574 for ; Fri, 23 Apr 2021 15:34:20 -0700 (PDT) Received: by mail-qk1-x74a.google.com with SMTP id k12-20020a05620a0b8cb02902e028cc62baso15546656qkh.17 for ; Fri, 23 Apr 2021 15:34:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=reply-to:date:in-reply-to:message-id:mime-version:references :subject:from:to:cc; bh=W0FsZgKrGD/FRL2xwnIckJkdwWI7yxmbTghAbdzf5Sc=; b=Iyor596ihpz1j4rciZ/W2f1ON2t53sv+AVrjqaO7ZAAOAj+be+Hxk+i+OTmgVYMxGh 2EijwHDTftvNRbPG2Sy+dJXc0laVixVeqZR5JDfwN4O4KwOuUuBykwVMK7iTNWRGu/Nh UDQBlv2QSrZBagAG2E4Xk5QY7G8tvsOwDs8owCFlEM8NAv2P44wOZGT7KCkk1n4Wi5cD Aqp6d1mmZEf7dIdRjV5CRYhqq7I4SPe0gn0ovzD11xeA29kRGdRUoU+rv2DVc8hYAZhU 3/H1rsTQrhhU2MglUGXd5LJPCOJwlQlRCyd1hnNXYGJeuzJYZee++l0hxRWG4NfQct4H sGjg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:reply-to:date:in-reply-to:message-id :mime-version:references:subject:from:to:cc; bh=W0FsZgKrGD/FRL2xwnIckJkdwWI7yxmbTghAbdzf5Sc=; b=scfRz8g90Z9BAvBg2AjGzcFNyRRBJDbAfuLZYNayZvjWCjEro4IK/7jtdgqVcvdgwb BqKQjtHLo+RlW/CPdrP3mVy4sGrijbTHyQmc5sSIxL4wATzEQ4TO3jGnWalhBA+FPNPg MIPyjj7woi0B48pqVgzloBDfQHKckMGb0iah7Y4ETNJddCfZvtvGmzFLGiMZ+ucXQoBN 6isMSW55Ogy/vSSfWwN9360OBFH8zvwjDS9hItkL5eN3gJEq37YlDGVJOSk19uxPiPuy J/36Si6KmFHb7kQ+s7YdwHfz2uN/NXBv4pHztE00+iYfRgzlp4sr3PUBHWVzi4qSlISJ e4dQ== X-Gm-Message-State: AOAM532J8s9aWGwKIqkkyHTaOMx9/JXK93b8VlSnCBIj3g7qnmPnyQDy 5OiUmQUA1XoN+8CYLsyatlzIxb9hZAM= X-Google-Smtp-Source: ABdhPJwKOk1AWyr9bMoQUdeSREhAWALjm4o4jVWciBFB9eOEw+sue3i6ihgCZu89/JCQ6XK93XsNX28Hzhg= X-Received: from seanjc798194.pdx.corp.google.com ([2620:15c:f:10:ad52:3246:e190:f070]) (user=seanjc job=sendgmr) by 2002:a05:6214:a8d:: with SMTP id ev13mr6868770qvb.23.1619217259300; Fri, 23 Apr 2021 15:34:19 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 23 Apr 2021 15:34:04 -0700 In-Reply-To: <20210423223404.3860547-1-seanjc@google.com> Message-Id: <20210423223404.3860547-5-seanjc@google.com> Mime-Version: 1.0 References: <20210423223404.3860547-1-seanjc@google.com> X-Mailer: git-send-email 2.31.1.498.g6c1eba8ee3d-goog Subject: [PATCH v3 4/4] KVM: SVM: Delay restoration of host MSR_TSC_AUX until return to userspace From: Sean Christopherson To: Paolo Bonzini Cc: Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Reiji Watanabe Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Use KVM's "user return MSRs" framework to defer restoring the host's MSR_TSC_AUX until the CPU returns to userspace. Add/improve comments to clarify why MSR_TSC_AUX is intercepted on both RDMSR and WRMSR, and why it's safe for KVM to keep the guest's value loaded even if KVM is scheduled out. Cc: Reiji Watanabe Signed-off-by: Sean Christopherson --- arch/x86/kvm/svm/svm.c | 52 +++++++++++++++++++----------------------- arch/x86/kvm/svm/svm.h | 7 ------ 2 files changed, 23 insertions(+), 36 deletions(-) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 4c7604fca009..a4bd7cb19755 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -213,6 +213,15 @@ struct kvm_ldttss_desc { DEFINE_PER_CPU(struct svm_cpu_data *, svm_data); +/* + * Only MSR_TSC_AUX is switched via the user return hook. EFER is switched via + * the VMCB, and the SYSCALL/SYSENTER MSRs are handled by VMLOAD/VMSAVE. + * + * RDTSCP and RDPID are not used in the kernel, specifically to allow KVM to + * defer the restoration of TSC_AUX until the CPU returns to userspace. + */ +#define TSC_AUX_URET_SLOT 0 + static const u32 msrpm_ranges[] = {0, 0xc0000000, 0xc0010000}; #define NUM_MSR_MAPS ARRAY_SIZE(msrpm_ranges) @@ -958,6 +967,9 @@ static __init int svm_hardware_setup(void) kvm_tsc_scaling_ratio_frac_bits = 32; } + if (boot_cpu_has(X86_FEATURE_RDTSCP)) + kvm_define_user_return_msr(TSC_AUX_URET_SLOT, MSR_TSC_AUX); + /* Check for pause filtering support */ if (!boot_cpu_has(X86_FEATURE_PAUSEFILTER)) { pause_filter_count = 0; @@ -1423,19 +1435,10 @@ static void svm_prepare_guest_switch(struct kvm_vcpu *vcpu) { struct vcpu_svm *svm = to_svm(vcpu); struct svm_cpu_data *sd = per_cpu(svm_data, vcpu->cpu); - unsigned int i; if (svm->guest_state_loaded) return; - /* - * Certain MSRs are restored on VMEXIT (sev-es), or vmload of host save - * area (non-sev-es). Save ones that aren't so we can restore them - * individually later. - */ - for (i = 0; i < NR_HOST_SAVE_USER_MSRS; i++) - rdmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]); - /* * Save additional host state that will be restored on VMEXIT (sev-es) * or subsequent vmload of host save area. @@ -1454,29 +1457,15 @@ static void svm_prepare_guest_switch(struct kvm_vcpu *vcpu) } } - /* This assumes that the kernel never uses MSR_TSC_AUX */ if (static_cpu_has(X86_FEATURE_RDTSCP)) - wrmsrl(MSR_TSC_AUX, svm->tsc_aux); + kvm_set_user_return_msr(TSC_AUX_URET_SLOT, svm->tsc_aux, -1ull); svm->guest_state_loaded = true; } static void svm_prepare_host_switch(struct kvm_vcpu *vcpu) { - struct vcpu_svm *svm = to_svm(vcpu); - unsigned int i; - - if (!svm->guest_state_loaded) - return; - - /* - * Certain MSRs are restored on VMEXIT (sev-es), or vmload of host save - * area (non-sev-es). Restore the ones that weren't. - */ - for (i = 0; i < NR_HOST_SAVE_USER_MSRS; i++) - wrmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]); - - svm->guest_state_loaded = false; + to_svm(vcpu)->guest_state_loaded = false; } static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu) @@ -2785,6 +2774,7 @@ static int svm_set_vm_cr(struct kvm_vcpu *vcpu, u64 data) static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) { struct vcpu_svm *svm = to_svm(vcpu); + int r; u32 ecx = msr->index; u64 data = msr->data; @@ -2888,11 +2878,15 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) break; case MSR_TSC_AUX: /* - * This is rare, so we update the MSR here instead of using - * direct_access_msrs. Doing that would require a rdmsr in - * svm_vcpu_put. + * TSC_AUX is usually changed only during boot and never read + * directly. Intercept TSC_AUX instead of exposing it to the + * guest via direct_access_msrs, and switch it via user return. */ - wrmsrl(MSR_TSC_AUX, svm->tsc_aux); + preempt_disable(); + r = kvm_set_user_return_msr(TSC_AUX_URET_SLOT, data, -1ull); + preempt_enable(); + if (r) + return 1; svm->tsc_aux = data; break; diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h index d6206196eec1..5d8027e9c1c5 100644 --- a/arch/x86/kvm/svm/svm.h +++ b/arch/x86/kvm/svm/svm.h @@ -23,11 +23,6 @@ #define __sme_page_pa(x) __sme_set(page_to_pfn(x) << PAGE_SHIFT) -static const u32 host_save_user_msrs[] = { - MSR_TSC_AUX, -}; -#define NR_HOST_SAVE_USER_MSRS ARRAY_SIZE(host_save_user_msrs) - #define IOPM_SIZE PAGE_SIZE * 3 #define MSRPM_SIZE PAGE_SIZE * 2 @@ -129,8 +124,6 @@ struct vcpu_svm { u64 next_rip; - u64 host_user_msrs[NR_HOST_SAVE_USER_MSRS]; - u64 spec_ctrl; /* * Contains guest-controlled bits of VIRT_SPEC_CTRL, which will be