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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 =?iso-8859-1?Q?Wei=DFschuh?= , 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 Message-ID: <20241121110242.GD24774@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 7257540009 X-Stat-Signature: kdqitjokjg3o6q8oqu4zrckgd7fbu9bo X-Rspam-User: X-HE-Tag: 1732186939-745597 X-HE-Meta: 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 r3txIEUC qXU5sR4Kly7wtZnsPZRfciGXPHaV6oONGiGK4xphpHQyOdAD6r06QBBA+Ydw9NWVI9YyJieNHSdUpLu3dOdAFApBw04zwAY7kpYfOPqgCGTKx+Dei/5ShC5qVA38RxLguXpCUjhUSMcaKFu1OAUPvlJh6gBgm9YBRP1DpdpKm4VIqgHLVEV9AQz66LaNH80d9l/TJ92Z7qpeejMSdUX4zz4N6/+XEuaxNsSQobMkGTUmWnI/C7OQN1wnQ5xOA7+8vw/OjBvivzfSjyVOPFXyafO+q2XEOc6x4PKmX53hDFs0sGPjLxphnOrsYsQ== 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 Wed, Nov 20, 2024 at 05:34:32PM +0100, Valentin Schneider wrote: > 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? > > There is however this: > > kvm_arch_vcpu_load() > `\ > mark_tsc_unstable() > > So plugging a VCPU might do that. Right, but that only happens if it observes the TSC doing dodgy, so that's deserved and shouldn't happen on hardware from this decade, and possibly the one before that.