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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B1A2BC433EF for ; Tue, 16 Nov 2021 01:08:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9BF86615E6 for ; Tue, 16 Nov 2021 01:08:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377480AbhKPBK5 (ORCPT ); Mon, 15 Nov 2021 20:10:57 -0500 Received: from mail.kernel.org ([198.145.29.99]:44608 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245422AbhKOTUc (ORCPT ); Mon, 15 Nov 2021 14:20:32 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2D77563279; Mon, 15 Nov 2021 18:34:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1637001268; bh=CQSKUf1FIsmfQk4kNQrCV7N2DYfkDGG2NHnpMk/XQk0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PqLn2ETASVoYEwQH5mOdGU98Buf//vX45tTq7A6/qpDhMFSOZKYGYr6jGXH0MgQTZ wbnj/uImqrvKPHeqd6eZEwMsSEqoNSpiVcLd/JHSMeIaSpDGAvc/mKQIRJ6nrnNU7S waec6NBp5WZhfs9hBLWfM5mfel2zVudw6CkTZqbk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sean Christopherson , Paolo Bonzini Subject: [PATCH 5.15 124/917] KVM: nVMX: Query current VMCS when determining if MSR bitmaps are in use Date: Mon, 15 Nov 2021 17:53:39 +0100 Message-Id: <20211115165432.954145609@linuxfoundation.org> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211115165428.722074685@linuxfoundation.org> References: <20211115165428.722074685@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: linux-kernel@vger.kernel.org From: Sean Christopherson commit 7dfbc624eb5726367900c8d86deff50836240361 upstream. Check the current VMCS controls to determine if an MSR write will be intercepted due to MSR bitmaps being disabled. In the nested VMX case, KVM will disable MSR bitmaps in vmcs02 if they're disabled in vmcs12 or if KVM can't map L1's bitmaps for whatever reason. Note, the bad behavior is relatively benign in the current code base as KVM sets all bits in vmcs02's MSR bitmap by default, clears bits if and only if L0 KVM also disables interception of an MSR, and only uses the buggy helper for MSR_IA32_SPEC_CTRL. Because KVM explicitly tests WRMSR before disabling interception of MSR_IA32_SPEC_CTRL, the flawed check will only result in KVM reading MSR_IA32_SPEC_CTRL from hardware when it isn't strictly necessary. Tag the fix for stable in case a future fix wants to use msr_write_intercepted(), in which case a buggy implementation in older kernels could prove subtly problematic. Fixes: d28b387fb74d ("KVM/VMX: Allow direct access to MSR_IA32_SPEC_CTRL") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Message-Id: <20211109013047.2041518-2-seanjc@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/vmx/vmx.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -769,15 +769,15 @@ void vmx_update_exception_bitmap(struct /* * Check if MSR is intercepted for currently loaded MSR bitmap. */ -static bool msr_write_intercepted(struct kvm_vcpu *vcpu, u32 msr) +static bool msr_write_intercepted(struct vcpu_vmx *vmx, u32 msr) { unsigned long *msr_bitmap; int f = sizeof(unsigned long); - if (!cpu_has_vmx_msr_bitmap()) + if (!(exec_controls_get(vmx) & CPU_BASED_USE_MSR_BITMAPS)) return true; - msr_bitmap = to_vmx(vcpu)->loaded_vmcs->msr_bitmap; + msr_bitmap = vmx->loaded_vmcs->msr_bitmap; if (msr <= 0x1fff) { return !!test_bit(msr, msr_bitmap + 0x800 / f); @@ -6720,7 +6720,7 @@ static fastpath_t vmx_vcpu_run(struct kv * If the L02 MSR bitmap does not intercept the MSR, then we need to * save it. */ - if (unlikely(!msr_write_intercepted(vcpu, MSR_IA32_SPEC_CTRL))) + if (unlikely(!msr_write_intercepted(vmx, MSR_IA32_SPEC_CTRL))) vmx->spec_ctrl = native_read_msr(MSR_IA32_SPEC_CTRL); x86_spec_ctrl_restore_host(vmx->spec_ctrl, 0);