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=-16.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 06F68C43219 for ; Thu, 21 Jan 2021 00:08:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D8B25238A0 for ; Thu, 21 Jan 2021 00:08:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732671AbhAUAHP (ORCPT ); Wed, 20 Jan 2021 19:07:15 -0500 Received: from mail.kernel.org ([198.145.29.99]:42936 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732384AbhATWdA (ORCPT ); Wed, 20 Jan 2021 17:33:00 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6D05122473; Wed, 20 Jan 2021 22:31:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1611181917; bh=IZpZup+7UVJmyznAHqT5zPuIOVNplTanitrN87XcENQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=KwC0JeacdrJ9LXB4DLrYNvG1UWPLOKtQNEEHroZ40vf2MbOcwg7s6hpJbLR8Gy3WX XZFEYY4qiVIU4t+VPH9r0cDDDV6As1d8Wvt0aj4rBoixMdHeVUTvKsHLuIRGPNSQAk ArIZKhC3fvn4kEjz7zGv7kjliP8Ha8wjmrqwlw2cujiDjPvqEDuwjxIZdHB4JIkxpR hNxcwCwPhM/xfLC5L+JhXPj3zqYOU0qhTr/T34gD7tshp9okYz9F7uWqgd2FtO9x8m Y8llKWlB3aoo0LNjX8RQJsGHhGEAx74KdgSbBMDJKKH3caZZB+lY2ER3UYFXIWFjy2 kMk9itOxx3uug== Date: Thu, 21 Jan 2021 00:31:52 +0200 From: Jarkko Sakkinen To: Tianjia Zhang Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Sean Christopherson , x86@kernel.org, linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, Jia Zhang Subject: Re: [PATCH v2] x86/sgx: Fix free_cnt counting logic in epc section Message-ID: References: <20210120035320.19709-1-tianjia.zhang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210120035320.19709-1-tianjia.zhang@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On Wed, Jan 20, 2021 at 11:53:20AM +0800, Tianjia Zhang wrote: > Increase `section->free_cnt` in sgx_sanitize_section() is more > reasonable, which is called in ksgxd kernel thread, instead of This is lacking reasoning of why. /Jarkko > assigning it to epc section pages number at initialization. > Although this is unlikely to fail, these pages cannot be > allocated after initialization, and which need to be reset > by ksgxd. > > At the same time, taking section->lock could be moved inside > the !ret flow so that EREMOVE is done without holding the lock. > it's theoretically possible that ksgxd hasn't finished > sanitizing the EPC when userspace starts creating enclaves. > > Reported-by: Jia Zhang > Suggested-by: Sean Christopherson > Reviewed-by: Sean Christopherson > Signed-off-by: Tianjia Zhang > --- > arch/x86/kernel/cpu/sgx/main.c | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c > index c519fc5f6948..34a72a147983 100644 > --- a/arch/x86/kernel/cpu/sgx/main.c > +++ b/arch/x86/kernel/cpu/sgx/main.c > @@ -41,16 +41,18 @@ 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) > + > + /* needed for access to ->page_list: */ > + spin_lock(§ion->lock); > + > + if (!ret) { > list_move(&page->list, §ion->page_list); > - else > + section->free_cnt += 1; > + } else > list_move_tail(&page->list, &dirty); > > spin_unlock(§ion->lock); > @@ -646,7 +648,6 @@ static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size, > list_add_tail(§ion->pages[i].list, §ion->init_laundry_list); > } > > - section->free_cnt = nr_pages; > return true; > } > > -- > 2.19.1.3.ge56e4f7 > >