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=-15.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, USER_AGENT_SANE_1 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 203BEC433E0 for ; Thu, 11 Feb 2021 06:16:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E0E4464E77 for ; Thu, 11 Feb 2021 06:16:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229731AbhBKGQK (ORCPT ); Thu, 11 Feb 2021 01:16:10 -0500 Received: from out30-56.freemail.mail.aliyun.com ([115.124.30.56]:46330 "EHLO out30-56.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229451AbhBKGQF (ORCPT ); Thu, 11 Feb 2021 01:16:05 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R811e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04426;MF=tianjia.zhang@linux.alibaba.com;NM=1;PH=DS;RN=12;SR=0;TI=SMTPD_---0UOPaBHJ_1613024116; Received: from 30.27.210.10(mailfrom:tianjia.zhang@linux.alibaba.com fp:SMTPD_---0UOPaBHJ_1613024116) by smtp.aliyun-inc.com(127.0.0.1); Thu, 11 Feb 2021 14:15:17 +0800 Subject: Re: [PATCH v4 2/5] x86/sgx: Reduce the locking range in sgx_sanitize_section() To: Jarkko Sakkinen Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Sean Christopherson , Shuah Khan , x86@kernel.org, linux-sgx@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Jia Zhang References: <20210201132653.35690-1-tianjia.zhang@linux.alibaba.com> <20210201132653.35690-3-tianjia.zhang@linux.alibaba.com> From: Tianjia Zhang Message-ID: Date: Thu, 11 Feb 2021 14:15:16 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/3/21 6:00 AM, Jarkko Sakkinen wrote: > On Mon, Feb 01, 2021 at 09:26:50PM +0800, Tianjia Zhang wrote: >> The spin lock of sgx_epc_section only locks the page_list. The >> EREMOVE operation and init_laundry_list is not necessary in the >> protection range of the spin lock. This patch reduces the lock >> range of the spin lock in the function sgx_sanitize_section() >> and only protects the operation of the page_list. >> >> Suggested-by: Sean Christopherson >> Signed-off-by: Tianjia Zhang > > I'm not confident that this change has any practical value. > > /Jarkko > As a process executed during initialization, this optimization effect may not be obvious. If possible, this critical area can be moved outside to protect the entire while loop. Best regards, Tianjia >> --- >> arch/x86/kernel/cpu/sgx/main.c | 11 ++++------- >> 1 file changed, 4 insertions(+), 7 deletions(-) >> >> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c >> index c519fc5f6948..4465912174fd 100644 >> --- a/arch/x86/kernel/cpu/sgx/main.c >> +++ b/arch/x86/kernel/cpu/sgx/main.c >> @@ -41,20 +41,17 @@ static void sgx_sanitize_section(struct sgx_epc_section *section) >> if (kthread_should_stop()) >> return; >> >> - /* needed for access to ->page_list: */ >> - spin_lock(§ion->lock); >> - >> page = list_first_entry(§ion->init_laundry_list, >> struct sgx_epc_page, list); >> >> ret = __eremove(sgx_get_epc_virt_addr(page)); >> - if (!ret) >> + if (!ret) { >> + spin_lock(§ion->lock); >> list_move(&page->list, §ion->page_list); >> - else >> + spin_unlock(§ion->lock); >> + } else >> list_move_tail(&page->list, &dirty); >> >> - spin_unlock(§ion->lock); >> - >> cond_resched(); >> } >> >> -- >> 2.19.1.3.ge56e4f7 >> >>