From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 18907CCF9EB for ; Wed, 29 Oct 2025 10:31:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 64AE58E0062; Wed, 29 Oct 2025 06:31:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5FBF98E0045; Wed, 29 Oct 2025 06:31:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4EAD38E0062; Wed, 29 Oct 2025 06:31:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 3AE6E8E0045 for ; Wed, 29 Oct 2025 06:31:40 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id CAC27BB89A for ; Wed, 29 Oct 2025 10:31:39 +0000 (UTC) X-FDA: 84050785518.05.6272AC9 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf14.hostedemail.com (Postfix) with ESMTP id 04848100010 for ; Wed, 29 Oct 2025 10:31:37 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=mQHpiMhH; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf14.hostedemail.com: domain of frederic@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=frederic@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1761733898; a=rsa-sha256; cv=none; b=T4CCk9A/4hi8G5pCIAwg8wcwX2uEobG7TPidDyg2bHPVVHWl1G9aouKCuaqHGwasr0JTs8 RBwO+V6tDuEAn5kztpNehUF383oIe6rpUmTZefdCNQBUEScMuc+9SZ4KnU7L28qjZoLjCy zcoZUQmduCJKI9kDBwRhrEzRy9bzuAA= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=mQHpiMhH; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf14.hostedemail.com: domain of frederic@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=frederic@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1761733898; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=CTXnL9UXH/iauUvH958Y5ZTz4Dt6IJaJSNAQ122UEVg=; b=nDQDgor0xgOxrAdl+n56lFFqY80KA3dMG5iZGsPBif21snyHZNniwIbyqG5TyT/v51+6Sz DwpPzIeh2QjtjMdFY2bg52crWOBX62W+ozJ726w4VwMQhV22uLK6s77LFjk6wl2S4N+vMx b5N9oDkNrTDsKfBKhNVA/XBFoo6dXZs= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 09C6443A44; Wed, 29 Oct 2025 10:31:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5E4DAC116D0; Wed, 29 Oct 2025 10:31:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761733896; bh=Kk/z5xbjPIxTq926BScJO1YbAE6B21A/nQcvL+Stxjo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mQHpiMhHIipyykg71nO9gr0ccOWvAw3jtxADhT6O9/iW0PpIiw/qmz5zVTUW3oo0Y Yq4gg7lmHuk8qvkB8w7kGP3dJ/Es/yfXH9Z/5NpT3GdhmC3rdV4d9InuM6AE6YDHuy 66y1CBVkVJ47bCQATzwguaNY0rGy4czAnJJf2Xq0+TNv8MsAXP6t2uwOLwNqTFFpSC b93q4JO88FSbhgGajCQoNTlTc5GzNikQEX4E8U13MGQNOniIiwlNgiHYmZ4xaVekC8 PXMEnG8bUYp8VmovluQl1CaebknBe933wtZ0M/W93tFXssHpX/nRz8xuoWt5VU0UOX RCaW/NJFhcGtw== Date: Wed, 29 Oct 2025 11:31:34 +0100 From: Frederic Weisbecker To: Valentin Schneider 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 Message-ID: References: <20251010153839.151763-1-vschneid@redhat.com> <20251010153839.151763-28-vschneid@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Stat-Signature: p9hpbqf9mk975tmfs49jb8nb7aykktnt X-Rspamd-Queue-Id: 04848100010 X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1761733897-88143 X-HE-Meta: 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 uqf847Zr PMw6M4iWe2UnfhcA0AKyLdDNwTQUWTRzavMSzQ5xAGUoNh/u8805o8HBifD7Lnjlvmogbe6bTHqwlaFaVJ/tUueAYSXArf2tEP0PPq3cazPAko7UzwpIJ5I1ckVqwX1JoKkMYyDXzTusB+KoW9Km2xxN6QyYBTWwSgaZx5qFZFLGnKjaVbHYHtB7rTeUyLTW8rlJJb08WIxUw8clEPA/adNufjDJYgCM94BJsazF1cHUn7jQKfgwtXhfcqhJqsrSJx73Hr2TIMEkV//KtGa7dq6pL2Te0bCnIYRaNl5rUIG8nHK2ooXD0oM7WCA== 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: Le Wed, Oct 29, 2025 at 11:16:23AM +0100, Valentin Schneider a écrit : > On 28/10/25 16:59, Frederic Weisbecker wrote: > > Le Fri, Oct 10, 2025 at 05:38:37PM +0200, Valentin Schneider a écrit : > >> @@ -171,8 +172,27 @@ For 32-bit we have the following conventions - kernel 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 > >> + /* No point in doing this for housekeeping CPUs */ > >> + movslq PER_CPU_VAR(cpu_number), \scratch_reg > >> + bt \scratch_reg, tick_nohz_full_mask(%rip) > >> + jnc .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). Or just check housekeeping_overriden static key before everything. This one is enabled only if either nohz_full, isolcpus or cpuset isolated partition (well, it's on the way for the last one) are running, but those are all niche, which means you spare 99.999% kernel usecases. Thanks. > > > Thanks. > > > > -- > > Frederic Weisbecker > > SUSE Labs > > -- Frederic Weisbecker SUSE Labs