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[213.44.141.166]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7b48523f72bsm112716485a.104.2024.11.20.08.34.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Nov 2024 08:34:41 -0800 (PST) From: Valentin Schneider To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, x86@kernel.org, rcu@vger.kernel.org, linux-kselftest@vger.kernel.org, Steven Rostedt , Masami Hiramatsu , Jonathan Corbet , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Paolo Bonzini , Wanpeng Li , Vitaly Kuznetsov , Andy Lutomirski , Frederic Weisbecker , "Paul E. McKenney" , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , Lorenzo Stoakes , Josh Poimboeuf , Jason Baron , Kees Cook , Sami Tolvanen , Ard Biesheuvel , Nicholas Piggin , Juerg Haefliger , Nicolas Saenz Julienne , "Kirill A. Shutemov" , Nadav Amit , Dan Carpenter , Chuang Wang , Yang Jihong , Petr Mladek , "Jason A. Donenfeld" , Song Liu , Julian Pidancet , Tom Lendacky , Dionna Glaze , Thomas =?utf-8?Q?Wei=C3=9Fschuh?= , Juri Lelli , Marcelo Tosatti , Yair Podemsky , Daniel Wagner , Petr Tesarik Subject: Re: [RFC PATCH v3 08/15] sched/clock, x86: Make __sched_clock_stable forceful In-Reply-To: <20241120145904.GK19989@noisy.programming.kicks-ass.net> References: <20241119153502.41361-1-vschneid@redhat.com> <20241119153502.41361-9-vschneid@redhat.com> <20241120145904.GK19989@noisy.programming.kicks-ass.net> Date: Wed, 20 Nov 2024 17:34:32 +0100 Message-ID: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: iUdIcGrP03F023P5Qz5NEGwa6TZQUjm7cM8xJCd4WMc_1732120482 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Rspam-User: X-Rspamd-Queue-Id: 8C4B714000E X-Rspamd-Server: rspam01 X-Stat-Signature: dcm6kqqqeiqpmwx7pkgxbj7qbwqtkqat X-HE-Tag: 1732120446-833091 X-HE-Meta: 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 fAYry8/i plp5jfAmRkOXXVMbtoBAQ1+IyJ1YmJuHhnvjS/xYa0LJSGbDf6QxmShMxD+PwDqR38sPvmqdU3EZiGarPqbdP0F4EJF2hlA+yKefbkNlopJU+nrXB7ddKN9geuzStfUClRxonrIei00FJtc+FS+etrdZ/WyjHnfnwXmGUOczDEziyvbsxxjnh8+nXRYVn1aVL8h84JlVtLc9P0XKjiVmduIbNyWazVyegfCimjXYvAlvhJ5Ew0IJZ1Ad7Ysp2kZVUx75Gj+TH6p8/aF3XD0+rdC+AVyFxqt144N85ur0qxqg/nxTAJ5M1f1KP2lz5C+623YPy19KZ0iRs0Fl9M1OKz3jeNnrFQqdA1H8GVZetIi6qw384BLsGEVn7e/iAfAN8jrgIQW+0cfgfFg/W72kWYRZz+CyhplznfKT00TojYK02Lpc= 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 20/11/24 15:59, Peter Zijlstra wrote: > On Tue, Nov 19, 2024 at 04:34:55PM +0100, Valentin Schneider wrote: >> Later commits will cause objtool to warn about non __ro_after_init static >> keys being used in .noinstr sections in order to safely defer instruction >> patching IPIs targeted at NOHZ_FULL CPUs. >> >> __sched_clock_stable is used in .noinstr code, and can be modified at >> runtime (e.g. KVM module loading). Suppressing the text_poke_sync() IPI has > > Wait, what !? loading KVM causes the TSC to be marked unstable? Ah, maybe not, I saw the below but that's actually the x86 specific stuff and IIUC can only be builtin: kvm_init_platform() `\ kvmclock_init() `\ kvm_sched_clock_init() `\ clear_sched_clock_stable() There is however this: kvm_arch_vcpu_load() `\ mark_tsc_unstable() So plugging a VCPU might do that.