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Tue, 4 Mar 2025 14:11:40 +0000 (UTC) Date: Tue, 4 Mar 2025 15:11:34 +0100 From: Borislav Petkov To: Brendan Jackman Cc: Dave Hansen , Rik van Riel , x86@kernel.org, linux-kernel@vger.kernel.org, peterz@infradead.org, dave.hansen@linux.intel.com, zhengqi.arch@bytedance.com, nadav.amit@gmail.com, thomas.lendacky@amd.com, kernel-team@meta.com, linux-mm@kvack.org, akpm@linux-foundation.org, jannh@google.com, mhklinux@outlook.com, andrew.cooper3@citrix.com, Manali.Shukla@amd.com, mingo@kernel.org Subject: Re: [PATCH v14 11/13] x86/mm: do targeted broadcast flushing from tlbbatch code Message-ID: <20250304141134.GIZ8cKFom3W0ChHiXk@fat_crate.local> References: <20250226030129.530345-1-riel@surriel.com> <20250226030129.530345-12-riel@surriel.com> <20250303114618.GBZ8WWihMDjf-oy8P0@fat_crate.local> <7e1ca8c7-6f3e-44dc-9dd8-bd273a03a83e@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam02 X-Stat-Signature: soy1891ia7tfkaypeg5wgusmhmk6bd7y X-Rspamd-Queue-Id: D805A16001C X-Rspam-User: X-HE-Tag: 1741097527-971246 X-HE-Meta: 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 yPk3DVtN 8pTgHMTUfGTOn78/q3K0galafLBbNeUvFATFalJQ0r1GQ0ljAgDnnRz88T8xmJMig+9twkkLCiVzD91C0cbKDEIhYO/lkB2Z8pMM0Nrv1DP9A4JvqLvn/vejxznHCs/qiR2IA6L7NhMq39rRnJKxnrOw0qFVgnAJh5svJxjHSWz+F9peb1PaLDBypNf1RGvqhqdOvIsdoqSxsWGk9Qp4K/iJ3N8amVe1qgXbQ9FsRLds2CfbYCtYTBm3J2yqADKaq/LojObpv0HDNw4mDolz2rEc56ONvgKk5KGPhLst+y9LWufQRi9aK4xDZqjbO2gNSPozkMlWWlWw5QX130KE0C00fYDBSit7S8J9+HmAuUk9Wlyw= 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 Tue, Mar 04, 2025 at 12:52:47PM +0000, Brendan Jackman wrote: > https://lore.kernel.org/all/CA+i-1C31TrceZiizC_tng_cc-zcvKsfXLAZD_XDftXnp9B2Tdw@mail.gmail.com/ Lemme try to understand what you're suggesting on that subthread: > static inline void arch_start_context_switch(struct task_struct *prev) > { > arch_paravirt_start_context_switch(prev); > tlb_start_context_switch(prev); > } This kinda makes sense to me... > Now I think about it... if we always tlbsync() before a context switch, is the > cant_migrate() above actually required? I think with that, even if we migrated > in the middle of e.g. broadcast_kernel_range_flush(), we'd be fine? (At > least, from the specific perspective of the invplgb code, presumably having > preemption on there would break things horribly in other ways). I think we still need it because you need to TLBSYNC on the same CPU you've issued the INVLPGB and actually, you want all TLBs to have been synched system-wide. Or am I misunderstanding it? Anything else I missed? Btw, I just sent v15 - if you wanna continue commenting there... https://lore.kernel.org/r/20250304135816.12356-1-bp@kernel.org Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette