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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 CD417C433E6 for ; Tue, 26 Jan 2021 16:12:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A6E3521E92 for ; Tue, 26 Jan 2021 16:12:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391403AbhAZQMY (ORCPT ); Tue, 26 Jan 2021 11:12:24 -0500 Received: from mga11.intel.com ([192.55.52.93]:1690 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2403926AbhAZQFa (ORCPT ); Tue, 26 Jan 2021 11:05:30 -0500 IronPort-SDR: /JfHikwDSfEdOacNyOqKHSUll4dt+N0iZvtJqVPWy9jPp6imrr3wu651wthQgh4rZwmy2qUn3T 3eCx3SD5EfuQ== X-IronPort-AV: E=McAfee;i="6000,8403,9876"; a="176413932" X-IronPort-AV: E=Sophos;i="5.79,375,1602572400"; d="scan'208";a="176413932" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jan 2021 08:04:38 -0800 IronPort-SDR: syfrDdNL14eOwtMAhmqv70Yeyx20dYlltSmmu1ixHLNOv7NL0MnEXdBFSOXgsVi3EKeVfCi/O6 QYsEB0VtLRXQ== X-IronPort-AV: E=Sophos;i="5.79,375,1602572400"; d="scan'208";a="369146692" Received: from ekfraser-mobl1.amr.corp.intel.com (HELO [10.209.173.94]) ([10.209.173.94]) by orsmga002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jan 2021 08:04:34 -0800 Subject: Re: [RFC PATCH v3 04/27] x86/sgx: Wipe out EREMOVE from sgx_free_epc_page() To: Kai Huang , linux-sgx@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org Cc: seanjc@google.com, 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: 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: 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 1/26/21 1:30 AM, Kai Huang wrote: > From: Jarkko Sakkinen > > Encapsulate the snippet in sgx_free_epc_page() concerning EREMOVE to > sgx_reset_epc_page(), which is a static helper function for > sgx_encl_release(). It's the only function existing, which deals with > initialized pages. Yikes. I have no idea what that is saying. Here's a rewrite: EREMOVE takes a pages and removes any association between that page and an enclave. It must be run on a page before it can be added into another enclave. Currently, EREMOVE is run as part of pages being freed into the SGX page allocator. It is not expected to fail. KVM does not track how guest pages are used, which means that SGX virtualization use of EREMOVE might fail. Break out the EREMOVE call from the SGX page allocator. This will allow the SGX virtualization code to use the allocator directly. (SGX/KVM will also introduce a more permissive EREMOVE helper). > diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c > index ee50a5010277..a78b71447771 100644 > --- a/arch/x86/kernel/cpu/sgx/encl.c > +++ b/arch/x86/kernel/cpu/sgx/encl.c > @@ -389,6 +389,16 @@ const struct vm_operations_struct sgx_vm_ops = { > .access = sgx_vma_access, > }; > > + > +static void sgx_reset_epc_page(struct sgx_epc_page *epc_page) > +{ > + int ret; > + > + ret = __eremove(sgx_get_epc_virt_addr(epc_page)); > + if (WARN_ONCE(ret, "EREMOVE returned %d (0x%x)", ret, ret)) > + return; > +} > + > /** > * sgx_encl_release - Destroy an enclave instance > * @kref: address of a kref inside &sgx_encl > @@ -412,6 +422,7 @@ void sgx_encl_release(struct kref *ref) > if (sgx_unmark_page_reclaimable(entry->epc_page)) > continue; > > + sgx_reset_epc_page(entry->epc_page); > sgx_free_epc_page(entry->epc_page); > encl->secs_child_cnt--; > entry->epc_page = NULL; > @@ -423,6 +434,7 @@ void sgx_encl_release(struct kref *ref) > xa_destroy(&encl->page_array); > > if (!encl->secs_child_cnt && encl->secs.epc_page) { > + sgx_reset_epc_page(encl->secs.epc_page); > sgx_free_epc_page(encl->secs.epc_page); > encl->secs.epc_page = NULL; > } > @@ -431,6 +443,7 @@ void sgx_encl_release(struct kref *ref) > va_page = list_first_entry(&encl->va_pages, struct sgx_va_page, > list); > list_del(&va_page->list); > + sgx_reset_epc_page(va_page->epc_page); > sgx_free_epc_page(va_page->epc_page); > kfree(va_page); > } > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c > index f330abdb5bb1..21c2ffa13870 100644 > --- a/arch/x86/kernel/cpu/sgx/main.c > +++ b/arch/x86/kernel/cpu/sgx/main.c > @@ -598,16 +598,14 @@ struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim) > * sgx_free_epc_page() - Free an EPC page > * @page: an EPC page > * > - * Call EREMOVE for an EPC page and insert it back to the list of free pages. > + * Put the EPC page back to the list of free pages. It's the callers "caller's" > + * responsibility to make sure that the page is in uninitialized state In other Period after "state", please. > + * words, do EREMOVE, EWB or whatever operation is necessary before calling > + * this function. > */ OK, so if you're going to say "the caller must put the page in uninitialized state", let's also add a comment to the place that *DO* that, like the shiny new sgx_reset_epc_page().