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 60DE9C433EF for ; Fri, 7 Jan 2022 18:55:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231840AbiAGSz2 (ORCPT ); Fri, 7 Jan 2022 13:55:28 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:58981 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231370AbiAGSzX (ORCPT ); Fri, 7 Jan 2022 13:55:23 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1641581722; 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: in-reply-to:in-reply-to:references:references; bh=xMFcYcH2Msh4EkPVql69cwVr+T1SO7BufToboxIymYY=; b=Zv9Kr3/8IJe9srhR1emrNMuJ92Ek4aY1f5nufpuVA0u6PyOp4niqFVZVFCoSh5M+GQRtYw 5NpPmrIJcQ0G/TCpzwpILXLYkqp0/gT+ePcKuFYBgV4tmjd6B6zM+iWxwuBqdZ5d2grhh+ FWgRfloNej9W1pxSkH8Y3qpoabCZJMM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-361-5KN4ryjoPf-DRc4fo5zpzQ-1; Fri, 07 Jan 2022 13:55:19 -0500 X-MC-Unique: 5KN4ryjoPf-DRc4fo5zpzQ-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 B087B81EE63; Fri, 7 Jan 2022 18:55:17 +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 065CC838F0; Fri, 7 Jan 2022 18:55:16 +0000 (UTC) From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: guang.zeng@intel.com, jing2.liu@intel.com, kevin.tian@intel.com, seanjc@google.com, tglx@linutronix.de, wei.w.wang@intel.com, yang.zhong@intel.com Subject: [PATCH v6 04/21] kvm: x86: Exclude unpermitted xfeatures at KVM_GET_SUPPORTED_CPUID Date: Fri, 7 Jan 2022 13:54:55 -0500 Message-Id: <20220107185512.25321-5-pbonzini@redhat.com> In-Reply-To: <20220107185512.25321-1-pbonzini@redhat.com> References: <20220107185512.25321-1-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: linux-kernel@vger.kernel.org From: Jing Liu KVM_GET_SUPPORTED_CPUID should not include any dynamic xstates in CPUID[0xD] if they have not been requested with prctl. Otherwise a process which directly passes KVM_GET_SUPPORTED_CPUID to KVM_SET_CPUID2 would now fail even if it doesn't intend to use a dynamically enabled feature. Userspace must know that prctl is required and allocate >4K xstate buffer before setting any dynamic bit. Suggested-by: Paolo Bonzini Signed-off-by: Jing Liu Signed-off-by: Yang Zhong Message-Id: <20220105123532.12586-5-yang.zhong@intel.com> Signed-off-by: Paolo Bonzini --- Documentation/virt/kvm/api.rst | 4 ++++ arch/x86/kvm/cpuid.c | 9 ++++++--- 2 files changed, 10 insertions(+), 3 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 6b683dfea8f2..f4ea5e41a4d0 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -1687,6 +1687,10 @@ userspace capabilities, and with user requirements (for example, the user may wish to constrain cpuid to emulate older hardware, or for feature consistency across a cluster). +Dynamically-enabled feature bits need to be requested with +``arch_prctl()`` before calling this ioctl. Feature bits that have not +been requested are excluded from the result. + Note that certain capabilities, such as KVM_CAP_X86_DISABLE_EXITS, may expose cpuid features (e.g. MONITOR) which are not supported by kvm in its default configuration. If userspace enables such capabilities, it diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index f3e6fda6b858..eb52dde5deec 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -815,11 +815,13 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) goto out; } break; - case 0xd: - entry->eax &= supported_xcr0; + case 0xd: { + u64 guest_perm = xstate_get_guest_group_perm(); + + entry->eax &= supported_xcr0 & guest_perm; entry->ebx = xstate_required_size(supported_xcr0, false); entry->ecx = entry->ebx; - entry->edx &= supported_xcr0 >> 32; + entry->edx &= (supported_xcr0 & guest_perm) >> 32; if (!supported_xcr0) break; @@ -866,6 +868,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) entry->edx = 0; } break; + } case 0x12: /* Intel SGX */ if (!kvm_cpu_cap_has(X86_FEATURE_SGX)) { -- 2.31.1