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Mon, 29 Jun 2026 09:05:15 -0400 (EDT) Date: Mon, 29 Jun 2026 14:05:14 +0100 From: Kiryl Shutsemau To: Catalin Marinas Cc: Will Deacon , James Morse , Mark Rutland , Marc Zyngier , Doug Anderson , Petr Mladek , Thomas Gleixner , Andrew Morton , Baoquan He , Puranjay Mohan , Usama Arif , Breno Leitao , Julien Thierry , Lecopzer Chen , Sumit Garg , kernel-team@meta.com, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 0/4] arm64: cross-CPU NMI via SDEI Message-ID: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Jun 26, 2026 at 08:40:57PM +0100, Kiryl Shutsemau wrote: > But I have not tried calling CPU_OFF directly, without completing the > event. I assumed it is required. Will give it a try when I have time. Tried it now, and it doesn't work either -- in a more interesting way. Calling PSCI CPU_OFF directly from the SDEI handler (event left uncompleted) reproducibly breaks the kdump capture kernel, and this reproduces under QEMU's TF-A, not just on Grace -- so it isn't a Grace firmware quirk. The test: a CPU wedged with interrupts masked is stopped via the SDEI rung; its handler calls __cpu_try_die() instead of parking. A/B in QEMU, changing only that wedged CPU's handling (everything else identical): - park it (current series): capture kernel boots fully to a shell. - CPU_OFF from the handler: capture kernel hangs in early boot, around SDEI re-init, never reaches a shell. Powering the PE off while its SDEI event is still active leaves EL3's dispatch state dangling, and the capture kernel trips over it. Completing the event first and then CPU_OFF -- what I tried originally -- silently wedges EL3 on Grace instead. So both routes off fail, and the CPU stays parked. The dump is complete either way; only re-onlining the stopped CPU in an SMP capture kernel is lost. It's a cheap QEMU repro now if anyone wants to dig into the EL3 side. -- Kiryl Shutsemau / Kirill A. Shutemov