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[213.44.135.146]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-429952b7b43sm25828786f8f.6.2025.10.29.03.16.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Oct 2025 03:16:25 -0700 (PDT) From: Valentin Schneider To: Frederic Weisbecker Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, rcu@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Arnaldo Carvalho de Melo , Josh Poimboeuf , Paolo Bonzini , Arnd Bergmann , "Paul E. McKenney" , Jason Baron , Steven Rostedt , Ard Biesheuvel , Sami Tolvanen , "David S. Miller" , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Mel Gorman , Andrew Morton , Masahiro Yamada , Han Shen , Rik van Riel , Jann Horn , Dan Carpenter , Oleg Nesterov , Juri Lelli , Clark Williams , Yair Podemsky , Marcelo Tosatti , Daniel Wagner , Petr Tesarik Subject: Re: [RFC PATCH v6 27/29] x86/mm/pti: Implement a TLB flush immediately after a switch to kernel CR3 In-Reply-To: References: <20251010153839.151763-1-vschneid@redhat.com> <20251010153839.151763-28-vschneid@redhat.com> Date: Wed, 29 Oct 2025 11:16:23 +0100 Message-ID: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: W5avLDHD3xPj2duhvsbSC-ljnvTWUsuCVyEVaiwmV5k_1761732986 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 5934340009 X-Rspamd-Server: rspam03 X-Stat-Signature: unhtcgnooq9ba9icy7rrdfegx34mrxip X-HE-Tag: 1761732991-708786 X-HE-Meta: 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 mtE9stfK 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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 28/10/25 16:59, Frederic Weisbecker wrote: > Le Fri, Oct 10, 2025 at 05:38:37PM +0200, Valentin Schneider a =C3=A9crit= : >> @@ -171,8 +172,27 @@ For 32-bit we have the following conventions - kern= el is built with >> andq $(~PTI_USER_PGTABLE_AND_PCID_MASK), \reg >> .endm >> >> -.macro COALESCE_TLBI >> +.macro COALESCE_TLBI scratch_reg:req >> #ifdef CONFIG_COALESCE_TLBI >> +=09/* No point in doing this for housekeeping CPUs */ >> +=09movslq PER_CPU_VAR(cpu_number), \scratch_reg >> +=09bt=09\scratch_reg, tick_nohz_full_mask(%rip) >> +=09jnc=09.Lend_tlbi_\@ > > I assume it's not possible to have a static call/branch to > take care of all this ? > I think technically yes, but that would have to be a per-cpu patchable location, which would mean something like each CPU having its own copy of that text page... Unless there's some existing way to statically optimize if (cpumask_test_cpu(smp_processor_id(), mask)) where @mask is a boot-time constant (i.e. the nohz_full mask). > Thanks. > > -- > Frederic Weisbecker > SUSE Labs