Re: [PATCH v5 00/25] context_tracking,x86: Defer some IPIs until a user->kernel transition

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To: Valentin Schneider <vschneid@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, virtualization@xxxxxxxxxxxxxxx, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, loongarch@xxxxxxxxxxxxxxx, linux-riscv@xxxxxxxxxxxxxxxxxxx, linux-perf-users@xxxxxxxxxxxxxxx, kvm@xxxxxxxxxxxxxxx, linux-arch@xxxxxxxxxxxxxxx, linux-modules@xxxxxxxxxxxxxxx, linux-trace-kernel@xxxxxxxxxxxxxxx, rcu@xxxxxxxxxxxxxxx, linux-hardening@xxxxxxxxxxxxxxx, linux-kselftest@xxxxxxxxxxxxxxx, bpf@xxxxxxxxxxxxxxx

Subject: Re: [PATCH v5 00/25] context_tracking,x86: Defer some IPIs until a user->kernel transition

From: Dave Hansen <dave.hansen@xxxxxxxxx>

Date: Tue, 29 Apr 2025 09:11:57 -0700

Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>, Marcelo Tosatti <mtosatti@xxxxxxxxxx>, Yair Podemsky <ypodemsk@xxxxxxxxxx>, Josh Poimboeuf <jpoimboe@xxxxxxxxxx>, Daniel Wagner <dwagner@xxxxxxx>, Petr Tesarik <ptesarik@xxxxxxxx>, Nicolas Saenz Julienne <nsaenz@xxxxxxxxxx>, Frederic Weisbecker <frederic@xxxxxxxxxx>, "Paul E. McKenney" <paulmck@xxxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, Sean Christopherson <seanjc@xxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Ajay Kaher <ajay.kaher@xxxxxxxxxxxx>, Alexey Makhalov <alexey.amakhalov@xxxxxxxxxxxx>, Broadcom internal kernel review list <bcm-kernel-feedback-list@xxxxxxxxxxxx>, Russell King <linux@xxxxxxxxxxxxxxx>, Catalin Marinas <catalin.marinas@xxxxxxx>, Will Deacon <will@xxxxxxxxxx>, Huacai Chen <chenhuacai@xxxxxxxxxx>, WANG Xuerui <kernel@xxxxxxxxxx>, Paul Walmsley <paul.walmsley@xxxxxxxxxx>, Palmer Dabbelt <palmer@xxxxxxxxxxx>, Albert Ou <aou@xxxxxxxxxxxxxxxxx>, Alexandre Ghiti <alex@xxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, x86@xxxxxxxxxx, "H. Peter Anvin" <hpa@xxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>, Namhyung Kim <namhyung@xxxxxxxxxx>, Mark Rutland <mark.rutland@xxxxxxx>, Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>, Jiri Olsa <jolsa@xxxxxxxxxx>, Ian Rogers <irogers@xxxxxxxxxx>, Adrian Hunter <adrian.hunter@xxxxxxxxx>, "Liang, Kan" <kan.liang@xxxxxxxxxxxxxxx>, Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>, Paolo Bonzini <pbonzini@xxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, Jason Baron <jbaron@xxxxxxxxxx>, Steven Rostedt <rostedt@xxxxxxxxxxx>, Ard Biesheuvel <ardb@xxxxxxxxxx>, Luis Chamberlain <mcgrof@xxxxxxxxxx>, Petr Pavlu <petr.pavlu@xxxxxxxx>, Sami Tolvanen <samitolvanen@xxxxxxxxxx>, Daniel Gomez <da.gomez@xxxxxxxxxxx>, Naveen N Rao <naveen@xxxxxxxxxx>, Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, Masami Hiramatsu <mhiramat@xxxxxxxxxx>, Neeraj Upadhyay <neeraj.upadhyay@xxxxxxxxxx>, Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>, Josh Triplett <josh@xxxxxxxxxxxxxxxx>, Boqun Feng <boqun.feng@xxxxxxxxx>, Uladzislau Rezki <urezki@xxxxxxxxx>, Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>, Lai Jiangshan <jiangshanlai@xxxxxxxxx>, Zqiang <qiang.zhang1211@xxxxxxxxx>, Vincent Guittot <vincent.guittot@xxxxxxxxxx>, Dietmar Eggemann <dietmar.eggemann@xxxxxxx>, Ben Segall <bsegall@xxxxxxxxxx>, Mel Gorman <mgorman@xxxxxxx>, Kees Cook <kees@xxxxxxxxxx>, Shuah Khan <shuah@xxxxxxxxxx>, Masahiro Yamada <masahiroy@xxxxxxxxxx>, Alice Ryhl <aliceryhl@xxxxxxxxxx>, Miguel Ojeda <ojeda@xxxxxxxxxx>, "Mike Rapoport (Microsoft)" <rppt@xxxxxxxxxx>, Rong Xu <xur@xxxxxxxxxx>, Rafael Aquini <aquini@xxxxxxxxxx>, Song Liu <song@xxxxxxxxxx>, Andrii Nakryiko <andrii@xxxxxxxxxx>, Dan Carpenter <dan.carpenter@xxxxxxxxxx>, Brian Gerst <brgerst@xxxxxxxxx>, "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>, Benjamin Berg <benjamin.berg@xxxxxxxxx>, Vishal Annapurve <vannapurve@xxxxxxxxxx>, Randy Dunlap <rdunlap@xxxxxxxxxxxxx>, John Stultz <jstultz@xxxxxxxxxx>, Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>

In-reply-to: <20250429113242.998312-1-vschneid@redhat.com>

References: <20250429113242.998312-1-vschneid@redhat.com>

User-agent: Mozilla Thunderbird

I don't think we should do this series.

If folks want this functionality, they should get a new CPU that can
flush the TLB without IPIs.