From nobody Sat Feb 7 04:07:13 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; dkim=fail; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=linaro.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1530023883833367.91398218848633; Tue, 26 Jun 2018 07:38:03 -0700 (PDT) Received: from localhost ([::1]:53100 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fXp6X-0001tt-1X for importer@patchew.org; Tue, 26 Jun 2018 10:38:01 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45610) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fXp4N-0000qN-55 for qemu-devel@nongnu.org; Tue, 26 Jun 2018 10:35:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fXp4J-0005nG-94 for qemu-devel@nongnu.org; Tue, 26 Jun 2018 10:35:47 -0400 Received: from mail-wr0-x235.google.com ([2a00:1450:400c:c0c::235]:39968) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1fXp4I-0005mm-Kp for qemu-devel@nongnu.org; Tue, 26 Jun 2018 10:35:43 -0400 Received: by mail-wr0-x235.google.com with SMTP id g18-v6so17510795wro.7 for ; Tue, 26 Jun 2018 07:35:42 -0700 (PDT) Received: from zen.linaro.local ([81.128.185.34]) by smtp.gmail.com with ESMTPSA id o17-v6sm1995601wrp.62.2018.06.26.07.35.40 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 26 Jun 2018 07:35:40 -0700 (PDT) Received: from zen.linaroharston (localhost [127.0.0.1]) by zen.linaro.local (Postfix) with ESMTP id 191453E01DB; Tue, 26 Jun 2018 15:35:40 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=hs2wOBTm+KB0y6OTQlHrynkBztfYpfwyGvLd0ouTB18=; b=VJV+awDUmEVgtSnGwhQh64Oe2XT2K1szMaLlRB7b0ZZzIKSMo4R5bnWoAoF/fgGNRI hqTnh3T2mZdZ2AfOM0Nd6Cj/hgPoF0oSTgXq+7kc5nFqEWISiLAuVmcYlMd0Y5IBNcxl dI+MivUx4sGkRQH/JaNr/B8kr9TOWmH1pB9lM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=hs2wOBTm+KB0y6OTQlHrynkBztfYpfwyGvLd0ouTB18=; b=bC8xvJhC3jQ03/biDqynpv0iiqtFxJSTuqhDuMYmmgwdQuKhhacz+ljjvs0b8IcH7m BGQpv0NcmrG/ula2NspA/IzJqGGrfK9/RnlcvXSvXpVNmk+LzdkKjkhPQnGqSZcPT5tD D5BRP3gO3KacNMI9c8h9QuwSxdPqEpml5gOcjMCLg7XJprZ22laSqzXhbFRqgYgMn0Vy +a0gqAJW4VTh/9dZlGu4XDzPvZXFJfXGnkMsBrQ1VfTL8TuXp33OhsTTcLSpsz0vSSBc cYugFtQWVU2n5m6rsp5KUdoBRBki4M7OE0vi2a3gfvOS/q3XuNE3WVpZJQ2Q7Ezz62w5 /oGg== X-Gm-Message-State: APt69E2M05tkg7Op5+y0PJIqLeX8aTEv1YRxI+HIwyhPUQjyQtrfVtJo 07BUFldvAVo+wDlMzo6i1G+jrQ== X-Google-Smtp-Source: AAOMgpfFYhZ0IzCqiiJulhuppms007mTZxbT40jkCpkLMP0d2pMNOLjzfXKBpKv3Zkpt11jYjdNz3g== X-Received: by 2002:adf:a581:: with SMTP id g1-v6mr1792365wrc.233.1530023741334; Tue, 26 Jun 2018 07:35:41 -0700 (PDT) From: =?UTF-8?q?Alex=20Benn=C3=A9e?= To: qemu-devel@nongnu.org Date: Tue, 26 Jun 2018 15:35:38 +0100 Message-Id: <20180626143538.5390-1-alex.bennee@linaro.org> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2a00:1450:400c:c0c::235 Subject: [Qemu-devel] [PATCH] blogposts: add post about the new check-tcg infrastructure X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: pbonzini@redhat.com, =?UTF-8?q?Alex=20Benn=C3=A9e?= Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZohoMail: RDKM_2 RSF_0 Z_629925259 SPT_0 Signed-off-by: Alex Benn=C3=A9e --- v2 - changes to the language for the lesser known architectures --- _posts/2018-06-21-tcg-testing.md | 139 +++++++++++++++++++++++++++++++ 1 file changed, 139 insertions(+) create mode 100644 _posts/2018-06-21-tcg-testing.md diff --git a/_posts/2018-06-21-tcg-testing.md b/_posts/2018-06-21-tcg-testi= ng.md new file mode 100644 index 0000000..dfc504c --- /dev/null +++ b/_posts/2018-06-21-tcg-testing.md @@ -0,0 +1,139 @@ +--- +layout: post +title: "QEMU TCG Tests" +date: 2018-06-21 10:30:00:00 +0000 +last_modified_at: 2018-06-21 10:30:00:00 +0000 +author: Alex Benn=C3=A9e +categories: [testing, docker, compilation, tcg] +--- + +Ever since I started working on QEMU there was a small directory +called tests/tcg that was in a perpetually broken state. It contains +tests that exercise QEMU's ability to work across architectures using +the power of the Tiny Code Generator. However as these tests needed to +be compiled for the *guest* architectures and not the *host* +architecture - known as cross-compiling - most developers never ran +them. As the tests were hardly ever built inevitably a certain amount +of bit-rot set in. + +# Cross Compilers + +In the old days cross-compilation setups were almost all hand-crafted +affairs which involved building versions of binutils, gcc and a basic +libc. If you couldn't get someone to give you a pre-built tarball it +was something you laboured through once and hopefully never had to +touch again. There were even dedicated scripts like crosstool-ng which +attempted to make the process of patching and configuring your +toolchain easier. + +While the distributions have improved their support for cross +compilers over the years there are still plenty of variations in how +they are deployed. It is hard for a project like QEMU which has to +build on a wide range of operating systems and architectures to +seamlessly use any given distributions compiler setup. However for +those with cross compilers to hand `configure` now accepts two +additional flags: + + --cross-cc-$(ARCH) + --cross-cc-flags-$(ARCH) + +With a compiler specified for each guest architecture you want to test +the build system can now build and run the tests. However for +developers that don't have cross compilers around they can now take +advantage of QEMU's docker images. + +# Enter Docker Containers + +If you work in IT you would be hard pressed not to have noticed the +hype around Docker and the concept of containerisation over the last +few years. Put simply containers allow you to define a known working +set of software that gets run in an isolated environment for a given +task. While this has many uses for QEMU it allows us to define build +environments that any developer can run without having to mess around +with their preferred host setup. + +Over the last few years QEMU's build system has been expanding the +number of docker images it supports. Most of this has been in service +of our CI testing such as [Patchew](https://patchew.org/QEMU/) and +[Shippable](https://app.shippable.com/github/qemu/qemu/dashboard) but +any developer with a docker setup can run the exact same images. For +example if you want to check your patches won't break when compiled on +a 32 bit ARM system you can run: + + make docker-test-build@debian-armhf-cross J=3Dn + +instead of tracking down a piece of ARM hardware to actually build on. +Run `make docker` in your source tree to see the range of builds and +tests it can support. + +# make check-tcg + +With the latest work [merged into +master](https://git.qemu.org/?p=3Dqemu.git;a=3Dcommit;h=3Dde44c044420d1139= 480fa50c2d5be19223391218) we can now +take advantage of both hand configured and docker based cross +compilers to build test cases for TCG again. To run the TCG tests +after you have built QEMU: + + make check-tcg + +and the build system will build and run all the tests it can for your +configured targets. + +# Rules for tests/tcg + +So now we have the infrastructure in place to add new tests what rules +need to be followed to add new tests?=20 + +Well the first thing to note is currently all the tests are for +linux-user versions of QEMU. This means the tests are all currently +user-space tests that have access to the Linux syscall ABI. + +Another thing to note is the tests are standalone from the rest of the +QEMU test infrastructure. To keep things simple they are compiled as +standalone "static" binaries. As the cross-compilation setup can be +quite rudimentary for some of the rarer architectures we only compile +against a standard libc. There is no support for linking to other +libraries like for example glib. Thread and maths support is part of +glibc so shouldn't be a problem. + +Finally when writing new tests consider if it really is architecture +specific or can be added to `tests/tcg/multiarch`. The multiarch tests +are re-built for every supported architecture and should be the +default place for anything explicitly testing syscalls and other +common parts of the code base. + +# What's Next + +My hope with this work is we can start adding more tests to +systematically defend functionality in linux-user. In fact I hope the +first port of call to reproducing a crash would be writing a test case +that can be added to our growing library of tests. + +Another thing that needs sorting out is getting toolchains for all of +the less common architectures. The current work relies heavily on the +excellent work of the Debian toolchain team in making multiarch +aware cross compilers available in their distribution. However QEMU +supports a lot more architectures than QEMU, some only as system +emulations. In principle supporting them is as easy as adding another +docker recipe but it might be these recipes end up having to compile +the compilers from source. + +The `tests/tcg` directory still contains a number of source files we +don't build.=20 + +The cris and openrisc directories contain user-space tests which just +need the support of a toolchain and the relevant Makefile plumbing to +be added. + +The lm32, mips and xtensa targets have a set of tests that need a +system emulator. Aside from adding the compilers as docker images some +additional work is needed to handle the differences between plain +linux-user tests which can simply return an exit code to getting the +results from a qemu-system emulation. Some architectures have +semi-hosting support already for this while others report their test +status over a simple serial link which will need to be parsed and +handled in custom versions of the +[`run-%:`](https://git.qemu.org/?p=3Dqemu.git;a=3Dblob;f=3Dtests/tcg/Makef= ile;h=3Dbf064153900a438e4ad8e2d79eaaac8a27d66062;hb=3DHEAD#l95) +rule. + + --=20 2.17.1