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 39B12CCF9E0 for ; Tue, 28 Oct 2025 15:59:23 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 989BB8016F; Tue, 28 Oct 2025 11:59:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 939A18013F; Tue, 28 Oct 2025 11:59:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8024E8016F; Tue, 28 Oct 2025 11:59:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 6B6F98013F for ; Tue, 28 Oct 2025 11:59:22 -0400 (EDT) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 1EDB31A04A2 for ; Tue, 28 Oct 2025 15:59:22 +0000 (UTC) X-FDA: 84047982564.25.AD3DA7A Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf11.hostedemail.com (Postfix) with ESMTP id 82A5940013 for ; Tue, 28 Oct 2025 15:59:20 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=h0Rjdky4; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf11.hostedemail.com: domain of frederic@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=frederic@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1761667160; a=rsa-sha256; cv=none; b=x6Q191kM6jWQsqn3OEHa2Cx9WYbQ97qh+OfdktOjchCX5Tml5C0CyH6a0XO55MclXrgmMB qKSVz/iuLDyHXGzpGmlcE3590+PZhP6xaWhS1T4gwV9FSLRV7F15VX5KOs8VpB1f3A9KWe ao/vOovarSbL35U519dtshY3iuJDQQo= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=h0Rjdky4; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf11.hostedemail.com: domain of frederic@kernel.org designates 172.105.4.254 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=1761667160; 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=eQvOkt2E+3y+uo1WdteSodshUamGy1TODkc+zOeJre8=; b=RbaIGe9WxTLt8vm50pieXpzzIXdSZzAKEUtv3qMgOGjOK5FJqChPXB8QrKzPvketshocgA yVb3ecAN3M0Fjtw+SPA5BMoOW9rVrDbkprKpuK86nAHwvpTcVlkEsXOMnxmil4JXln3S6n VDbU2mIcH3bjeIWTN2zgyqLRcKUjaWw= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 9D8A8614A7; Tue, 28 Oct 2025 15:59:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C55CEC4CEE7; Tue, 28 Oct 2025 15:59:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761667159; bh=SDRIuqWM2TI7GYT8HdCkn7TBcJvTMa+nGGBd4kxLWaU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=h0Rjdky40XtCVRjoUUWv5rLiJ9ZMpCagJKFXeyfzHOGEHTGw9bKgoBDki9igeNVWF hxxzLvARw99/t5f4Lqs+Dj5fZyVuN3fZZCRfCFM55ZeACJS/rijOr6rAqCQE7Hwid1 QyXcKn0xMZDkHD1ajCbuYBSCn+ENYdvO5PJWUuqfmfteG28nQwGE4UO2KHjBeLwl2c hE32PRBdNnuYpqH0YyIEEpoBXAGIkGRuRSDfPq/9QdewsKj3LtsQ6g4eJFxD5TaKJO HpEpDWwMqwcXSfnux9kuKahgFba9EgaGpASx7PAIM38ag+Pw/+fgAan6RlnvKpPKM4 jLUxM6PBiYL0w== Date: Tue, 28 Oct 2025 16:59:16 +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: <20251010153839.151763-28-vschneid@redhat.com> X-Stat-Signature: eomw6fh5jjaa4yy8zkkf55zzqu7se9ih X-Rspamd-Queue-Id: 82A5940013 X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1761667160-292057 X-HE-Meta: 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 QB9QUq8p Cs9S0g0JUoar+QyNLUzPgftGMlXOTaUrxwefvHDyptuQPvozECvduNIPoG1IH3LDTGhOKKuoO3uKuxTDBHB8hyVxVobHQwEf9v+RLLoRAEe122pPgxQ5YTDnCoQmtZxQ+QKVDZ/71rmqcHJjRikfkNxeQ5amqSYDQitgJfxfLG7R/d2rcE1tzkgFdc3NAULnJ1aKLXwzmLQdOVcUY1YdLsZC0gkZzG0GTJPNLVY+6wpcfqXASbVhBxDF/YEhs5QnxDbjCT20WJrv2ZvQh5bMHB/xsXxkHX68JUDyNT2cenj1Ntg9oQy5YXwoZk+7LIsymWUQjmjxGUg1l8JvqwdpLntiQGg25iW5C3LYNbX2C4A/9FCtQafC7VmvDpw== 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 Fri, Oct 10, 2025 at 05:38:37PM +0200, Valentin Schneider a écrit : > Deferring kernel range TLB flushes requires the guarantee that upon > entering the kernel, no stale entry may be accessed. The simplest way to > provide such a guarantee is to issue an unconditional flush upon switching > to the kernel CR3, as this is the pivoting point where such stale entries > may be accessed. > > As this is only relevant to NOHZ_FULL, restrict the mechanism to NOHZ_FULL > CPUs. > > Note that the COALESCE_TLBI config option is introduced in a later commit, > when the whole feature is implemented. > > Signed-off-by: Valentin Schneider > --- > arch/x86/entry/calling.h | 26 +++++++++++++++++++++++--- > arch/x86/kernel/asm-offsets.c | 1 + > 2 files changed, 24 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h > index 813451b1ddecc..19fb6de276eac 100644 > --- a/arch/x86/entry/calling.h > +++ b/arch/x86/entry/calling.h > @@ -9,6 +9,7 @@ > #include > #include > #include > +#include > > /* > > @@ -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 ? Thanks. -- Frederic Weisbecker SUSE Labs