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([2600:1700:2442:6db0:6822:a477:b6d1:664a]) by smtp.gmail.com with ESMTPSA id x203-20020acae0d4000000b00383eaea5e88sm3266425oig.38.2023.03.13.09.02.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 13 Mar 2023 09:02:19 -0700 (PDT) Message-ID: <40299ee6-c518-5505-0dc5-874deef03d19@gmail.com> Date: Mon, 13 Mar 2023 11:02:17 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: [PATCH 2/8] of: Enable DTB loading on UML for KUnit tests Content-Language: en-US To: David Gow , Stephen Boyd Cc: Michael Turquette , linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org, patches@lists.linux.dev, Brendan Higgins , Greg Kroah-Hartman , "Rafael J . Wysocki" , Richard Weinberger , Anton Ivanov , Johannes Berg , Vincent Whitchurch , Rob Herring , Christian Marangi , Krzysztof Kozlowski , devicetree@vger.kernel.org, linux-um@lists.infradead.org, linux-kselftest@vger.kernel.org, kunit-dev@googlegroups.com References: <20230302013822.1808711-1-sboyd@kernel.org> <20230302013822.1808711-3-sboyd@kernel.org> From: Frank Rowand In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230313_090222_299743_4640EBA5 X-CRM114-Status: GOOD ( 43.26 ) X-BeenThere: linux-um@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-um" Errors-To: linux-um-bounces+linux-um=archiver.kernel.org@lists.infradead.org On 3/11/23 00:42, David Gow wrote: > On Sat, 11 Mar 2023 at 07:34, Stephen Boyd wrote: >> >> Quoting David Gow (2023-03-10 00:09:48) >>> On Fri, 10 Mar 2023 at 07:19, Stephen Boyd wrote: >>>> >>>> >>>> Hmm. I think you're suggesting that the unit test data be loaded >>>> whenever CONFIG_OF=y and CONFIG_KUNIT=y. Then tests can check for >>>> CONFIG_OF and skip if it isn't enabled? >>>> >>> >>> More of the opposite: that we should have some way of supporting tests >>> which might want to use a DTB other than the built-in one. Mostly for >>> non-UML situations where an actual devicetree is needed to even boot >>> far enough to get test output (so we wouldn't be able to override it >>> with a compiled-in test one). >> >> Ok, got it. >> >>> >>> I think moving to overlays probably will render this idea obsolete: >>> but the thought was to give test code a way to check for the required >>> devicetree nodes at runtime, and skip the test if they weren't found. >>> That way, the failure mode for trying to boot this on something which >>> required another device tree for, e.g., serial, would be "these tests >>> are skipped because the wrong device tree is loaded", not "I get no >>> output because serial isn't working". >>> >>> Again, though, it's only really needed for non-UML, and just loading >>> overlays as needed should be much more sensible anyway. >> >> I still have one niggle here. Loading overlays requires >> CONFIG_OF_OVERLAY, and the overlay loading API returns -ENOTSUPP when >> CONFIG_OF_OVERLAY=n. For now I'm checking for the config being enabled >> in each test, but I'm thinking it may be better to simply call >> kunit_skip() from the overlay loading function if the config is >> disabled. This way tests can simply call the overlay loading function >> and we'll halt the test immediately if the config isn't enabled. >> > > That sounds sensible, though there is a potential pitfall. If > kunit_skip() is called directly from overlay code, might introduce a > dependency on kunit.ko from the DT overlay, which we might not want. > The solution there is either to have a kunit wrapper function (so the > call is already in kunit.ko), or to have a hook to skip the current > test (which probably makes sense to do anyway, but I think the wrapper > is the better option). > > >>> >>>>> >>>>> That being said, I do think that there's probably some sense in >>>>> supporting the compiled-in DTB as well (it's definitely simpler than >>>>> patching kunit.py to always pass the extra command-line option in, for >>>>> example). >>>>> But maybe it'd be nice to have the command-line option override the >>>>> built-in one if present. >>>> >>>> Got it. I need to test loading another DTB on the commandline still, but >>>> I think this won't be a problem. We'll load the unittest-data DTB even >>>> with KUnit on UML, so assuming that works on UML right now it should be >>>> unchanged by this series once I resend. >>> >>> Again, moving to overlays should render this mostly obsolete, no? Or >>> am I misunderstanding how the overlay stuff will work? >> >> Right, overlays make it largely a moot issue. The way the OF unit tests >> work today is by grafting a DTB onto the live tree. I'm reusing that >> logic to graft a container node target for kunit tests to add their >> overlays too. It will be clearer once I post v2. >> >>> >>> One possible future advantage of being able to test with custom DTs at >>> boot time would be for fuzzing (provide random DT properties, see what >>> happens in the test). We've got some vague plans to support a way of >>> passing custom data to tests to support this kind of case (though, if >>> we're using overlays, maybe the test could just patch those if we >>> wanted to do that). >> >> Ah ok. I can see someone making a fuzzer that modifies devicetree >> properties randomly, e.g. using different strings for clock-names. >> >> This reminds me of another issue I ran into. I wanted to test adding the >> same platform device to the platform bus twice to confirm that the >> second device can't be added. That prints a warning, which makes >> kunit.py think that the test has failed because it printed a warning. Is >> there some way to avoid that? I want something like >> >> KUNIT_EXPECT_WARNING(test, ) >> >> so I can test error cases. DT unittests already have a similar concept. A test can report that a kernel warning (or any other specific text) either (1) must occur for the test to pass or (2) must _not_ occur for the test to pass. The check for the kernel warning is done by the test output parsing program scripts/dtc/of_unittest_expect. The reporting by a test of an expected error in drivers/of/unittest.c is done by EXPECT_BEGIN() and EXPECT_END(). These have been in unittest for a long time. The reporting by a test of a not expected to occur error is done by EXPECT_NOT_BEGIN() and EXPECT_NOT_END(). These are added to unittest in linux 6.3-rc1. I discussed this concept in one of the early TAP / KTAP discussion threads and expect to start a discussion thread on this specific topic in the KTAP Specification V2 context. I expect the discussion to result in a different implementation than what DT unittests are using (bike shedding likely to ensue) but whatever is agreed to should be easy for DT to switch to. > > Hmm... I'd've thought that shouldn't be a problem: kunit.py should > ignore most messages during a test, unless it can't find a valid > result line. What does the raw KTAP output look like? (You can get it > from kunit.py by passing the --raw_output option). > > That being said, a KUNIT_EXPECT_LOG_MESSAGE() or similar is something > we've wanted for a while. I think that the KASAN folks have been > working on something similar using console tracepoints: > https://lore.kernel.org/all/ebf96ea600050f00ed567e80505ae8f242633640.1666113393.git.andreyknvl@google.com/ > > Cheers, > -- David _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um