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[209.85.128.51]) by smtp.gmail.com with ESMTPSA id qk34sm1677774ejc.143.2022.01.09.12.00.48 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 09 Jan 2022 12:00:49 -0800 (PST) Received: by mail-wm1-f51.google.com with SMTP id 2-20020a05600c02c200b003470f96e778so5849136wmn.5 for ; Sun, 09 Jan 2022 12:00:48 -0800 (PST) X-Received: by 2002:a05:600c:4f13:: with SMTP id l19mr19440706wmq.152.1641758075416; Sun, 09 Jan 2022 11:54:35 -0800 (PST) MIME-Version: 1.0 References: <7c9c388c388df8e88bb5d14828053ac0cb11cf69.1641659630.git.luto@kernel.org> <739A3109-04DD-4BA5-A02B-52EE30E820AE@gmail.com> <1B6896F0-7A51-4936-8B50-0B86551FA3B7@gmail.com> <803a5d61426b149abf08e19759e086893e379382.camel@surriel.com> <8C459519-AF2B-457F-8E99-8957BC1FB61F@gmail.com> In-Reply-To: <8C459519-AF2B-457F-8E99-8957BC1FB61F@gmail.com> From: Linus Torvalds Date: Sun, 9 Jan 2022 11:54:19 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 16/23] sched: Use lightweight hazard pointers to grab lazy mms To: Nadav Amit Cc: Rik van Riel , Andy Lutomirski , Andrew Morton , Linux-MM , Nicholas Piggin , Anton Blanchard , Benjamin Herrenschmidt , Paul Mackerras , Randy Dunlap , linux-arch , X86 ML , Dave Hansen , Peter Zijlstra , Mathieu Desnoyers Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 9D60D4000C X-Stat-Signature: fb5zaz7ekbr4qniew51sukco4q9qzz5d Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=JBUaczY3; spf=pass (imf01.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.208.47 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org; dmarc=none X-Rspamd-Server: rspam10 X-HE-Tag: 1641758452-865212 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: On Sun, Jan 9, 2022 at 11:51 AM Nadav Amit wrote: > > If you already accept PTI, [..] I really don't think anybody should ever "accept PTI". It's an absolutely enormous cost, and it should be seen as a last-choice thing. Only really meant for completely broken hardware (ie meltdown), and for people who have some very serious issues and think it's "reasonable" to have the TLB isolation. No real normal sane setup should ever "accept PTI", and it shouldn't be used as an argument. Linus