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Sun, 01 Nov 2026 09:29:05 -0800 (PST) Received: from localhost.localdomain ([2001:9e8:8c1a:8d00:4ed:aeed:5810:610b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4ab61d8b9f4sm254261355e9.12.2026.11.01.09.29.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 01 Nov 2026 09:29:04 -0800 (PST) From: Lorand Marton To: =?UTF-8?q?Alex=20Benn=C3=A9e?= Cc: qemu-devel@nongnu.org, qemu-arm@nongnu.org, Paolo Bonzini , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Peter Maydell , Richard Henderson , qemu-stable@nongnu.org Subject: Re: [PATCH 1/4] target/arm: hold bql when SEV sets the event_register Date: Sun, 1 Nov 2026 18:29:01 +0100 Message-ID: <20261101172901.873975-1-lorandmarton.dev@gmail.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261030141046.2710206-2-alex.bennee@linaro.org> References: <20261030141046.2710206-1-alex.bennee@linaro.org> <20261030141046.2710206-2-alex.bennee@linaro.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::32a; envelope-from=lorandmarton.dev@gmail.com; helo=mail-wm1-x32a.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 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Sun, 01 Nov 2026 12:57:46 -0500 X-BeenThere: qemu-arm@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_PASS,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Fri, 30 Oct 2026 at 14:10, Alex Bennée wrote: > There is a race in qemu_process_cpu_events and sleeping on halt_cond > where we can miss the setting of the event_register which would cause > arm_cpu_has_work to report we shouldn't sleep. As by definition the > bql has to be held when we go to sleep against halt_cond guard the > kicking of the cpus by the SEV helper with the BQL to ensure things > are properly serialised. I hit this race with a bare-metal test in which two CPUs pass a turn back and forth 500000 times with WFE and SEV (virt, -smp 2, semihosting). On master (af1179b406) it hangs in 10 of 10 runs with -cpu max and in 10 of 10 with cortex-a72 (no result after 20 s; a passing run takes 2 s). A second test, in which a CPU waits in WFE for a broadcast TLBI and an SEV, hangs in 23 of 100 runs with cortex-a53. With this series applied on the same master, the first test passes 150 of 150 runs (50 each with max, cortex-a72 and cortex-a53) and the second 600 of 600 (200 each). Tested-by: Lorand Marton The series has no test case now; I can post these two as tests/tcg/aarch64/system tests if that helps. Thanks, Lorand