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[213.44.141.166]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-39ac67970a2sm5909443f8f.16.2025.03.26.01.56.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Mar 2025 01:56:08 -0700 (PDT) From: Valentin Schneider To: Jann Horn , Rik van Riel Cc: Dave Hansen , 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 , Frederic Weisbecker , "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 29/30] x86/mm, mm/vmalloc: Defer flush_tlb_kernel_range() targeting NOHZ_FULL CPUs In-Reply-To: References: <20250114175143.81438-1-vschneid@redhat.com> <20250114175143.81438-30-vschneid@redhat.com> <352317e3-c7dc-43b4-b4cb-9644489318d0@intel.com> <408ebd8b-4bfb-4c4f-b118-7fe853c6e897@intel.com> Date: Wed, 26 Mar 2025 09:56:06 +0100 Message-ID: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 8_s8cMXv-8jYsX2VTEGzR1LW5K5AkrsTe2oSu7u3YeY_1742979370 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 428C840011 X-Stat-Signature: 5enepunik1b1hs5snq73zu835kfrpdhn X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1742979373-990188 X-HE-Meta: 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 rSs19dQ0 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 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 25/03/25 19:41, Jann Horn wrote: > On Tue, Mar 25, 2025 at 6:52=E2=80=AFPM Valentin Schneider wrote: >> On 20/02/25 09:38, Dave Hansen wrote: >> > But, honestly, I'm still not sure this is worth all the trouble. If >> > folks want to avoid IPIs for TLB flushes, there are hardware features >> > that *DO* that. Just get new hardware instead of adding this complicat= ed >> > pile of software that we have to maintain forever. In 10 years, we'll >> > still have this software *and* 95% of our hardware has the hardware >> > feature too. >> >> Sorry, you're going to have to deal with my ignorance a little bit longe= r... >> >> Were you thinking x86 hardware specifically, or something else? >> AIUI things like arm64's TLBIVMALLE1IS can do what is required without a= ny >> IPI: >> >> C5.5.78 >> """ >> The invalidation applies to all PEs in the same Inner Shareable shareabi= lity domain as the PE that >> executes this System instruction. >> """ >> >> But for (at least) these architectures: >> >> alpha >> x86 >> loongarch >> mips >> (non-freescale 8xx) powerpc >> riscv >> xtensa >> >> flush_tlb_kernel_range() has a path with a hardcoded use of on_each_cpu(= ), >> so AFAICT for these the IPIs will be sent no matter the hardware. > > On X86, both AMD and Intel have some fairly recently introduced CPU > features that can shoot down TLBs remotely. > > The patch series > > adds support for the AMD flavor; that series landed in the current > merge window (it's present in the mainline git repository now and should > be part of 6.15). I think support for the Intel flavor has not yet > been implemented, but the linked patch series mentions a plan to look > at the Intel flavor next. Thanks for the info!