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=-6.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 D2DF9C07E9C for ; Fri, 9 Jul 2021 16:22:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B8125613C5 for ; Fri, 9 Jul 2021 16:22:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229606AbhGIQZe (ORCPT ); Fri, 9 Jul 2021 12:25:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:56560 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229491AbhGIQZd (ORCPT ); Fri, 9 Jul 2021 12:25:33 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5CDA261153; Fri, 9 Jul 2021 16:22:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1625847769; bh=kxyDYP6A8O10FtJkUZON8yJOupFKIyAhOIelmPtwv5I=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bZeKzIiYXEGbK0b9C6iTSp+7gymmyaIyPpTJr+lJkFub5wqx75idU9eUzfu+AEgr8 +9onnivkg8BXgiatHW9u5VvmG7gIikAMaENxrGV5Qm+KgeG3PvNy5Za6UdoVX90h// 9W+qlDq/Kf+nnYgJwbyxZ7NmXZUZctfErCrsPkLkbo4NwFyFkzisCfZ/v3vwFLR+AD KrsQCi1sJf8fIk+kRe/zgTVlVHeftuzfGB14jEQNEdrgBfT7dEFLDT/IzIa831iykg hvPVEX+slJhPXeXdQqHgxAFr8dgVoZe8kB1YCid7b8DkE6Qi+ZOWDputyWTvcQC9uu bkoqM+CaGnN8Q== Date: Fri, 9 Jul 2021 19:22:47 +0300 From: Jarkko Sakkinen To: Reinette Chatre Cc: Shuah Khan , linux-kselftest@vger.kernel.org, linux-sgx@vger.kernel.org, Borislav Petkov , Dave Hansen , linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/4] selftests/sgx: Trigger the reclaimer and #PF handler Message-ID: <20210709162247.d5ggqgpqpu2drp6o@kernel.org> References: <20210705143652.116125-1-jarkko@kernel.org> <20210705143652.116125-5-jarkko@kernel.org> <715ed555-5044-6fee-1d09-1c4cfa827af3@intel.com> <20210706235016.uucukyrr3ckk57pi@kernel.org> <16505466-e001-c4b0-ec41-5384ddcf194b@intel.com> <20210707091736.6wzemgmtzuegk3uf@kernel.org> <10664754-7e53-d9d1-f00c-f9dbd4a2d877@intel.com> <20210707205019.6jy64s4uqcw65q4h@kernel.org> <64b1cac8-75b9-8549-8499-60b4d72cf9ef@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <64b1cac8-75b9-8549-8499-60b4d72cf9ef@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 07, 2021 at 02:20:04PM -0700, Reinette Chatre wrote: > Hi Jarkko, > > On 7/7/2021 1:50 PM, Jarkko Sakkinen wrote: > > On Wed, Jul 07, 2021 at 08:02:42AM -0700, Reinette Chatre wrote: > > > Hi Jarkko, > > > > > > On 7/7/2021 2:17 AM, Jarkko Sakkinen wrote: > > > > On Tue, Jul 06, 2021 at 05:10:38PM -0700, Reinette Chatre wrote: > > > > > Hi Jarkko, > > > > > > > > > > On 7/6/2021 4:50 PM, Jarkko Sakkinen wrote: > > > > > > On Tue, Jul 06, 2021 at 11:34:54AM -0700, Reinette Chatre wrote: > > > > > > > Hi Jarkko, > > > > > > > > > > > > > > On 7/5/2021 7:36 AM, Jarkko Sakkinen wrote: > > > > > > > > Create a heap for the test enclave, which has the same size as all > > > > > > > > available Enclave Page Cache (EPC) pages in the system. This will guarantee > > > > > > > > that all test_encl.elf pages *and* SGX Enclave Control Structure (SECS) > > > > > > > > have been swapped out by the page reclaimer during the load time. Actually, > > > > > > > > this adds a bit more stress than that since part of the EPC gets reserved > > > > > > > > for the Version Array (VA) pages. > > > > > > > > > > > > > > > > For each test, the page fault handler gets triggered in two occasions: > > > > > > > > > > > > > > > > - When SGX_IOC_ENCLAVE_INIT is performed, SECS gets swapped in by the > > > > > > > > page fault handler. > > > > > > > > - During the execution, each page that is referenced gets swapped in > > > > > > > > by the page fault handler. > > > > > > > > > > > > > > > > > > > > > > If I understand this correctly, all EPC pages are now being consumed during > > > > > > > fixture setup and thus every SGX test, no matter how big or small, now > > > > > > > becomes a stress test of the reclaimer instead of there being a unique > > > > > > > reclaimer test. Since an enclave is set up and torn down for every test this > > > > > > > seems like a significant addition. It also seems like this would impact > > > > > > > future tests of dynamic page addition where not all scenarios could be > > > > > > > tested with all EPC pages already consumed. > > > > > > > > > > > > > > Reinette > > > > > > > > > > > > Re-initializing the test enclave is mandatory thing to do for all tests > > > > > > because it has an internals state. > > > > > > > > > > > > > > > > Right, but not all tests require the same enclave. In kselftest terminology > > > > > I think you are attempting to force all tests to depend on the same test > > > > > fixture. Is it not possible to have a separate "reclaimer" test fixture that > > > > > would build an enclave with a large heap and then have reclaimer tests that > > > > > exercise it by being tests that are specific to this "reclaimer fixture"? > > > > > > > > > > Reinette > > > > > > > > Why add that complexity? > > > > > > > > > > With this change every test is turned into a pseudo reclaimer test without > > > there being any explicit testing (with pass/fail criteria) of reclaimer > > > behavior. This is an expensive addition and reduces the scenarios that the > > > tests can exercise. > > > > > > Reinette > > > > There is consistent known behaviour how reclaimer and also the page fault > > are exercised for each test. I think that is what matters most right now > > that the basic behaviour of both the page reclaimer and page fault handler > > gets exercised. > > I believe the basic behavior of page fault handler is currently exercised in > each test, this is required. This not true. The current test does not exercise ELDU code path. > > > > > I don't understand the real-world gain of doing something factors more > > complex than necessary at a particular point of time, when you don't > > really need to hang yourself into it forever. > > Your argument about "hang yourself into it forever" can go both ways - why > should all tests now unnecessarily consume the entire EPC forever? > > If I understand correctly adding a separate reclaimer test is not complex > but would require refactoring code. What does it matter anyway if code nees to be refactored? > > This patch does increase the coverage in a deterministic manner to the code > > paths that were not previously exercised, i.e. we know the code paths, and > > could even calculate the exact number of times that they are triggered. And > > without doing anything obscure. That's what matters to me. > > On the contrary this is indeed obfuscating the SGX tests: if an issue shows > up in the reclaimer then all tests would fail. If there is a unique > reclaimer test then that would help point to where the issue may be. I tend to disagree this. I'll add a separate reclaimer test if I need to test something that this does not scale. It's an iterative process. /Jarkko