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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 62E6DC433E6 for ; Thu, 7 Jan 2021 00:53:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 35C0523118 for ; Thu, 7 Jan 2021 00:53:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726645AbhAGAxY (ORCPT ); Wed, 6 Jan 2021 19:53:24 -0500 Received: from mga06.intel.com ([134.134.136.31]:4799 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725860AbhAGAxY (ORCPT ); Wed, 6 Jan 2021 19:53:24 -0500 IronPort-SDR: yIYDUmnHlITDy/mwQMemoglFbwzAquU2tw7blfKkttb8TIoXxeNjOnp8j6X/CJxweVhjKC7kCY DHV8OQbI3Heg== X-IronPort-AV: E=McAfee;i="6000,8403,9856"; a="238903775" X-IronPort-AV: E=Sophos;i="5.79,328,1602572400"; d="scan'208";a="238903775" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Jan 2021 16:52:50 -0800 IronPort-SDR: 5H+DcWD20BKP5VU1cmuCFTruUihbdrkmxMRuZYlpNkjABM7bNtZpcjPSe9DQ44UO6IcoFzt+wH xsTY+oG3XpdQ== X-IronPort-AV: E=Sophos;i="5.79,328,1602572400"; d="scan'208";a="422379432" Received: from jmonroe1-mobl2.amr.corp.intel.com (HELO [10.212.12.85]) ([10.212.12.85]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Jan 2021 16:52:49 -0800 Subject: Re: [RFC PATCH 03/23] x86/sgx: Introduce virtual EPC for use by KVM guests To: Kai Huang , Sean Christopherson Cc: linux-sgx@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org, jarkko@kernel.org, luto@kernel.org, haitao.huang@intel.com, pbonzini@redhat.com, bp@alien8.de, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com References: <2e424ff3-51cb-d6ed-6c5f-190e1d4fe21a@intel.com> <20210107134758.ba0b5d950282973eaefe1ded@intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210107134758.ba0b5d950282973eaefe1ded@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 1/6/21 4:47 PM, Kai Huang wrote: >>>> + ret = __eremove(sgx_get_epc_virt_addr(epc_page)); >>>> + if (ret) { >>>> + /* >>>> + * Only SGX_CHILD_PRESENT is expected, which is because of >>>> + * EREMOVE-ing an SECS still with child, in which case it can >>>> + * be handled by EREMOVE-ing the SECS again after all pages in >>>> + * virtual EPC have been EREMOVE-ed. See comments in below in >>>> + * sgx_virt_epc_release(). >>>> + */ >>>> + WARN_ON_ONCE(ret != SGX_CHILD_PRESENT); >>>> + return ret; >>>> + } >>> I find myself wondering what errors could cause the WARN_ON_ONCE() to be >>> hit. The SDM indicates that it's only: >>> >>> SGX_ENCLAVE_ACT If there are still logical processors executing >>> inside the enclave. >>> >>> Should that be mentioned in the comment? >> And faults, which are also spliced into the return value by the ENCLS macros. >> I do remember hitting this WARN when I broke things, though I can't remember >> whether it was a fault or the SGX_ENCLAVE_ACT scenario. Probably the latter? > I'll add a comment saying that there should be no active logical processor > still running inside guest's enclave. We cannot handle SGX_ENCLAVE_ACT here > anyway. One more thing... Could we dump out the *actual* error code with a WARN(), please? If we see a warning, I'd rather not have to disassemble the instructions and check against register values to see whether the error code was sane.