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charset=UTF-8 Date: Fri, 21 Jul 2023 23:55:38 +1000 Message-Id: Cc: , "Daniel Henrique Barboza" , =?utf-8?q?C=C3=A9dric_Le_Goater?= , "David Gibson" , "Greg Kurz" , "Harsh Prateek Bora" , "John Snow" , "Cleber Rosa" , "Pavel Dovgalyuk" , "Paolo Bonzini" , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , "Wainer dos Santos Moschetta" , "Beraldo Leal" , "Peter Maydell" , "Richard Henderson" Subject: Re: [PATCH 7/7] tests/avocado: ppc64 pseries reverse debugging test From: "Nicholas Piggin" To: "Nicholas Piggin" , "Pavel Dovgalyuk" , X-Mailer: aerc 0.15.2 References: <20230623125707.323517-1-npiggin@gmail.com> <20230623125707.323517-8-npiggin@gmail.com> <74691561-c288-abf5-9673-6e230d55b813@ispras.ru> In-Reply-To: Received-SPF: pass client-ip=2607:f8b0:4864:20::d2e; envelope-from=npiggin@gmail.com; helo=mail-io1-xd2e.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon Jun 26, 2023 at 7:34 PM AEST, Nicholas Piggin wrote: > On Mon Jun 26, 2023 at 5:49 PM AEST, Pavel Dovgalyuk wrote: > > On 23.06.2023 15:57, Nicholas Piggin wrote: > > > pseries can run reverse-debugging well enough to pass basic tests. > > >=20 > > > There is strangeness with reverse-continue possibly relating to a bp > > > being set on the first instruction or on a snapshot, that causes > > > the PC to be reported on the first instruction rather than last > > > breakpoint, so a workaround is added for that for now. > > > > It means that the test reveals some kind of a bug in PPC debugging=20 > > server implementation. > > In this case it is better to fix that instead of adding workaround. > > I agree, and I'm trying to find the cause it hasn't been easy. I > thought the test was still interesting because it otherwise seems > to work well, but hopefully I can find the issue before long. I found the problem after too much staring at record-replay. QEMU works perfectly, it is the ppc pseries firmware that branches to its own entry point address within the recorded trace, and that confuses the test script. I'm not sure the best way to work around it. Initial skip works okay but also maybe(?) a good edge case to test a break on the very first instruction of the trace even if we don't reverse continue to it. I will send a new series and propose to add the breakpoints before seeking to the end of the trace, so we will catch a breakpoint being executed again. Thanks, Nick