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=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 B708BC433DF for ; Mon, 19 Oct 2020 17:05:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 51CC8205ED for ; Mon, 19 Oct 2020 17:05:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="NFwUCbZ4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730897AbgJSRFc (ORCPT ); Mon, 19 Oct 2020 13:05:32 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:43801 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730635AbgJSRFb (ORCPT ); Mon, 19 Oct 2020 13:05:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1603127130; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=8T33BC/57dNGym7wEnyJvGdAxGs0P1jblpQACkcYHg0=; b=NFwUCbZ4jj4P5XxAO2BtNK7+hyi13lr2nyUtEJ+q3tHEuNSSK8q3QHtPtPtjdzdf7yp78K GRjATeZTDyOqPEbGNU97tvBLPdaFAZVN9sqZHcJmibdZ+z7pVSMr3K1z45hj1zcsQY61Uv oDNV2+97Y691Q/V1Xy0H/bHglExSees= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-162-tOZTp_APOFifK1536HR7MQ-1; Mon, 19 Oct 2020 13:05:26 -0400 X-MC-Unique: tOZTp_APOFifK1536HR7MQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 52903D6883; Mon, 19 Oct 2020 17:05:25 +0000 (UTC) Received: from virtlab701.virt.lab.eng.bos.redhat.com (virtlab701.virt.lab.eng.bos.redhat.com [10.19.152.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9E78F5C22A; Mon, 19 Oct 2020 17:05:19 +0000 (UTC) From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Alexander Graf , Aaron Lewis , Peter Xu , Sean Christopherson Subject: [PATCH] KVM: VMX: Forbid userspace MSR filters for x2APIC Date: Mon, 19 Oct 2020 13:05:19 -0400 Message-Id: <20201019170519.1855564-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Allowing userspace to intercept reads to x2APIC MSRs when APICV is fully enabled for the guest simply can't work. But more in general, if the LAPIC is in-kernel, allowing accessed by userspace would be very confusing. If userspace wants to intercept x2APIC MSRs, then it should first disable in-kernel APIC. We could in principle allow userspace to intercept reads and writes to TPR, and writes to EOI and SELF_IPI, but while that could be made it work, it would still be silly. Cc: Alexander Graf Cc: Aaron Lewis Cc: Peter Xu Cc: Sean Christopherson Signed-off-by: Paolo Bonzini --- arch/x86/kvm/x86.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index c4015a43cc8a..0faf733538f4 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5246,6 +5246,13 @@ static int kvm_add_msr_filter(struct kvm *kvm, struct kvm_msr_filter_range *user return r; } +static bool range_overlaps_x2apic(struct kvm_msr_filter_range *range) +{ + u32 start = range->base; + u32 end = start + range->nmsrs; + return start <= 0x8ff && end > 0x800; +} + static int kvm_vm_ioctl_set_msr_filter(struct kvm *kvm, void __user *argp) { struct kvm_msr_filter __user *user_msr_filter = argp; @@ -5257,6 +5264,16 @@ static int kvm_vm_ioctl_set_msr_filter(struct kvm *kvm, void __user *argp) if (copy_from_user(&filter, user_msr_filter, sizeof(filter))) return -EFAULT; + /* + * In principle it would be possible to trap x2apic ranges + * if !lapic_in_kernel. This however would be complicated + * because KVM_X86_SET_MSR_FILTER can be called before + * KVM_CREATE_IRQCHIP or KVM_ENABLE_CAP. + */ + for (i = 0; i < ARRAY_SIZE(filter.ranges); i++) + if (range_overlaps_x2apic(&filter.ranges[i])) + return -EINVAL; + kvm_clear_msr_filter(kvm); default_allow = !(filter.flags & KVM_MSR_FILTER_DEFAULT_DENY); -- 2.26.2