From patchwork Tue Aug 30 02:45:10 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Huang, Kai" X-Patchwork-Id: 12958629 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 B1E8FECAAD2 for ; Tue, 30 Aug 2022 02:45:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229453AbiH3Cpw (ORCPT ); Mon, 29 Aug 2022 22:45:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38214 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229472AbiH3Cpu (ORCPT ); Mon, 29 Aug 2022 22:45:50 -0400 Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9BC36659D3; Mon, 29 Aug 2022 19:45:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1661827548; x=1693363548; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=0TI8jQLapdOITPsRn4jkg5RomLHydJPJ4LzrJPCvLTI=; b=dN0sMA3b1PDc3u+/hv5AMp2KNzzChy+I7M6ejzyayR1h4yFsN8IMRAdl ToJwLCBtg3J7T1R55mb2CXb9zV0WrpmCsfyJvsa4BZJdm+kzExoIF9Y/M MtKQdm2Fm1N1cY751TaxDFbguLjEthQ30n99vT+g15TNCvOgG8drGaVy3 f1N3B8Nc5EfLDpdp9b2GItGjYc5I/07aXn40WN9mEpaCcE7Cq9x3niyO3 +x+R/YuGH7yowdvTun9m81q4NauUhuECyzVqR0CmqEuajaxpDocACvSJV cabRDZz3tmxLorIbPyCtRYszRFBakYNW/XDvRUHEFBNw48I/NYVUKSMFw w==; X-IronPort-AV: E=McAfee;i="6500,9779,10454"; a="296338703" X-IronPort-AV: E=Sophos;i="5.93,274,1654585200"; d="scan'208";a="296338703" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Aug 2022 19:45:48 -0700 X-IronPort-AV: E=Sophos;i="5.93,274,1654585200"; d="scan'208";a="939831538" Received: from yghanbar-mobl2.amr.corp.intel.com (HELO khuang2-desk.gar.corp.intel.com) ([10.213.185.134]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Aug 2022 19:45:43 -0700 From: Kai Huang To: linux-sgx@vger.kernel.org, kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, dave.hansen@linux.intel.com, seanjc@google.com, pbonzini@redhat.com, jarkko@kernel.org, haitao.huang@linux.intel.com Subject: [PATCH v3] KVM: VMX: Allow exposing EDECCSSA user leaf function to KVM guest Date: Tue, 30 Aug 2022 14:45:10 +1200 Message-Id: <20220830024510.68973-1-kai.huang@intel.com> X-Mailer: git-send-email 2.37.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org The new Asynchronous Exit (AEX) notification mechanism (AEX-notify) allows one enclave to receive a notification in the ERESUME after the enclave exit due to an AEX. EDECCSSA is a new SGX user leaf function (ENCLU[EDECCSSA]) to facilitate the AEX notification handling. The new EDECCSSA is enumerated via CPUID(EAX=0x12,ECX=0x0):EAX[11]. Besides Allowing reporting the new AEX-notify attribute to KVM guests, also allow reporting the new EDECCSSA user leaf function to KVM guests so the guest can fully utilize the AEX-notify mechanism. Similar to existing X86_FEATURE_SGX1 and X86_FEATURE_SGX2, introduce a new scattered X86_FEATURE_SGX_EDECCSSA bit for the new EDECCSSA, and report it in KVM's supported CPUIDs. Note, no additional KVM enabling is required to allow the guest to use EDECCSSA. It's impossible to trap ENCLU (without completely preventing the guest from using SGX). Advertise EDECCSSA as supported purely so that userspace doesn't need to special case EDECCSSA, i.e. doesn't need to manually check host CPUID. The inability to trap ENCLU also means that KVM can't prevent the guest from using EDECCSSA, but that virtualization hole is benign as far as KVM is concerned. EDECCSSA is simply a fancy way to modify internal enclave state. More background about how do AEX-notify and EDECCSSA work: SGX maintains a Current State Save Area Frame (CSSA) for each enclave thread. When AEX happens, the enclave thread context is saved to the CSSA and the CSSA is increased by 1. For a normal ERESUME which doesn't deliver AEX notification, it restores the saved thread context from the previously saved SSA and decreases the CSSA. If AEX-notify is enabled for one enclave, the ERESUME acts differently. Instead of restoring the saved thread context and decreasing the CSSA, it acts like EENTER which doesn't decrease the CSSA but establishes a clean slate thread context using the CSSA for the enclave to handle the notification. After some handling, the enclave must discard the "new-established" SSA and switch back to the previously saved SSA (upon AEX). Otherwise, the enclave will run out of SSA space upon further AEXs and eventually fail to run. To solve this problem, the new EDECCSSA essentially decreases the CSSA. It can be used by the enclave notification handler to switch back to the previous saved SSA when needed, i.e. after it handles the notification. Acked-by: Sean Christopherson Acked-by: Jarkko Sakkinen Signed-off-by: Kai Huang --- v2 -> v3: - Updated subsystem tag to "KVM: VMX:" (Sean). - Updated changelog (Sean). - Added Sean and Jarkko's Acks. --- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/kernel/cpu/cpuid-deps.c | 1 + arch/x86/kernel/cpu/scattered.c | 1 + arch/x86/kvm/cpuid.c | 2 +- arch/x86/kvm/reverse_cpuid.h | 3 +++ 5 files changed, 7 insertions(+), 1 deletion(-) base-commit: ee56a283988d739c25d2d00ffb22707cb487ab47 diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 235dc85c91c3..ccdd35adae9e 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -304,6 +304,7 @@ #define X86_FEATURE_UNRET (11*32+15) /* "" AMD BTB untrain return */ #define X86_FEATURE_USE_IBPB_FW (11*32+16) /* "" Use IBPB during runtime firmware calls */ #define X86_FEATURE_RSB_VMEXIT_LITE (11*32+17) /* "" Fill RSB on VM exit when EIBRS is enabled */ +#define X86_FEATURE_SGX_EDECCSSA (11*32+18) /* "" SGX EDECCSSA user leaf function */ /* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */ #define X86_FEATURE_AVX_VNNI (12*32+ 4) /* AVX VNNI instructions */ diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c index c881bcafba7d..d95221117129 100644 --- a/arch/x86/kernel/cpu/cpuid-deps.c +++ b/arch/x86/kernel/cpu/cpuid-deps.c @@ -75,6 +75,7 @@ static const struct cpuid_dep cpuid_deps[] = { { X86_FEATURE_SGX_LC, X86_FEATURE_SGX }, { X86_FEATURE_SGX1, X86_FEATURE_SGX }, { X86_FEATURE_SGX2, X86_FEATURE_SGX1 }, + { X86_FEATURE_SGX_EDECCSSA, X86_FEATURE_SGX1 }, { X86_FEATURE_XFD, X86_FEATURE_XSAVES }, { X86_FEATURE_XFD, X86_FEATURE_XGETBV1 }, { X86_FEATURE_AMX_TILE, X86_FEATURE_XFD }, diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c index fd44b54c90d5..0bb339857985 100644 --- a/arch/x86/kernel/cpu/scattered.c +++ b/arch/x86/kernel/cpu/scattered.c @@ -40,6 +40,7 @@ static const struct cpuid_bit cpuid_bits[] = { { X86_FEATURE_PER_THREAD_MBA, CPUID_ECX, 0, 0x00000010, 3 }, { X86_FEATURE_SGX1, CPUID_EAX, 0, 0x00000012, 0 }, { X86_FEATURE_SGX2, CPUID_EAX, 1, 0x00000012, 0 }, + { X86_FEATURE_SGX_EDECCSSA, CPUID_EAX, 11, 0x00000012, 0 }, { X86_FEATURE_HW_PSTATE, CPUID_EDX, 7, 0x80000007, 0 }, { X86_FEATURE_CPB, CPUID_EDX, 9, 0x80000007, 0 }, { X86_FEATURE_PROC_FEEDBACK, CPUID_EDX, 11, 0x80000007, 0 }, diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 75dcf7a72605..c21b4a5dc8fa 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -644,7 +644,7 @@ void kvm_set_cpu_caps(void) ); kvm_cpu_cap_init_scattered(CPUID_12_EAX, - SF(SGX1) | SF(SGX2) + SF(SGX1) | SF(SGX2) | SF(SGX_EDECCSSA) ); kvm_cpu_cap_mask(CPUID_8000_0001_ECX, diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h index a19d473d0184..4e5b8444f161 100644 --- a/arch/x86/kvm/reverse_cpuid.h +++ b/arch/x86/kvm/reverse_cpuid.h @@ -23,6 +23,7 @@ enum kvm_only_cpuid_leafs { /* Intel-defined SGX sub-features, CPUID level 0x12 (EAX). */ #define KVM_X86_FEATURE_SGX1 KVM_X86_FEATURE(CPUID_12_EAX, 0) #define KVM_X86_FEATURE_SGX2 KVM_X86_FEATURE(CPUID_12_EAX, 1) +#define KVM_X86_FEATURE_SGX_EDECCSSA KVM_X86_FEATURE(CPUID_12_EAX, 11) struct cpuid_reg { u32 function; @@ -78,6 +79,8 @@ static __always_inline u32 __feature_translate(int x86_feature) return KVM_X86_FEATURE_SGX1; else if (x86_feature == X86_FEATURE_SGX2) return KVM_X86_FEATURE_SGX2; + else if (x86_feature == X86_FEATURE_SGX_EDECCSSA) + return KVM_X86_FEATURE_SGX_EDECCSSA; return x86_feature; }