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[213.44.141.166]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38dbf2ed900sm12687106f8f.53.2025.02.10.09.36.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Feb 2025 09:36:24 -0800 (PST) From: Valentin Schneider To: Frederic Weisbecker Cc: linux-kernel@vger.kernel.org, x86@kernel.org, virtualization@lists.linux.dev, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, linux-perf-users@vger.kernel.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, linux-arch@vger.kernel.org, rcu@vger.kernel.org, linux-hardening@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, bpf@vger.kernel.org, bcm-kernel-feedback-list@broadcom.com, Juergen Gross , Ajay Kaher , Alexey Makhalov , Russell King , Catalin Marinas , Will Deacon , Huacai Chen , WANG Xuerui , Paul Walmsley , Palmer Dabbelt , Albert Ou , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Peter Zijlstra , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , "Liang, Kan" , Boris Ostrovsky , Josh Poimboeuf , Pawan Gupta , Sean Christopherson , Paolo Bonzini , Andy Lutomirski , Arnd Bergmann , "Paul E. McKenney" , Jason Baron , Steven Rostedt , Ard Biesheuvel , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Juri Lelli , Clark Williams , Yair Podemsky , Tomas Glozar , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Kees Cook , Andrew Morton , Christoph Hellwig , Shuah Khan , Sami Tolvanen , Miguel Ojeda , Alice Ryhl , "Mike Rapoport (Microsoft)" , Samuel Holland , Rong Xu , Nicolas Saenz Julienne , Geert Uytterhoeven , Yosry Ahmed , "Kirill A. Shutemov" , "Masami Hiramatsu (Google)" , Jinghao Jia , Luis Chamberlain , Randy Dunlap , Tiezhu Yang Subject: Re: [PATCH v4 22/30] context_tracking: Exit CT_STATE_IDLE upon irq/nmi entry In-Reply-To: References: <20250114175143.81438-1-vschneid@redhat.com> <20250114175143.81438-23-vschneid@redhat.com> Date: Mon, 10 Feb 2025 18:36:20 +0100 Message-ID: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 0gCPKfkcArZ5YfJgB99m5MfyrCnyvorIFqOD8azN0YI_1739208986 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 95B0120007 X-Rspamd-Server: rspam12 X-Stat-Signature: my7ak44gg55kpc3jy7rqbdhmzeyeiquu X-HE-Tag: 1739208988-797798 X-HE-Meta: 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 H+HPmaS7 2T9j7J3YOY2z8nMhsZp/zBq38Ed3cDdlFFH3hOHIdciAWAej7tVD7E5oQXa5210PEogNixBgTJkQNsfoY7Nb2BqOXqNJMRvwe4n93GVHlZgwjiWZFCj7AngWIXhpAKg0jRRFgBnw/ONP33pE9vYudGXmi+R6/ocrbJuyvdwnjdX87CANXWBwuXsDiDVAsKNVmVZEttCVG0AmJ32ybHHaXFtw/HusZBwrO32isPfUNTs5HVjY4aShcUicMz+FQGpHuKEVCtAkhST7C/4ITKSTjJmIJ4NXBaLRs2BY5AvoiNsA1Ks5dI8v2qQogl/sup85ZJakxevG4JCWJhwSXcUFtIcujFcUl3rOED8vpEEa15mY61WZutX3/7UAkoo2WRihQW98P/D8ChEgkqfRFiYqZHa6e8M9yF1Vy5K2Fn60cHRUYyrBKQb2Wh6Ux9+4jcNHfr539p4K81P3h0eE6YzjcPqp2rwx5D0i7NDSL X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 07/02/25 19:37, Frederic Weisbecker wrote: > Le Fri, Feb 07, 2025 at 06:06:45PM +0100, Valentin Schneider a =C3=A9crit= : >> >> Soooo I've been thinking... >> >> Isn't >> >> (context_tracking.state & CT_RCU_WATCHING) >> >> pretty much a proxy for knowing whether a CPU is executing in kernelspac= e, >> including NMIs? > > You got it! > Yay! >> >> NMI interrupts userspace/VM/idle -> ct_nmi_enter() -> it becomes true >> IRQ interrupts idle -> ct_irq_enter() -> it becomes true >> IRQ interrupts userspace -> __ct_user_exit() -> it becomes true >> IRQ interrupts VM -> __ct_user_exit() -> it becomes true >> >> IOW, if I gate setting deferred work by checking for this instead of >> explicitely CT_STATE_KERNEL, "it should work" and prevent the >> aforementioned issue? Or should I be out drinking instead? :-) > > Exactly it should work! Now that doesn't mean you can't go out > for a drink :-) > Well, drinks were had very shortly after sending this email :D > Thanks.