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 B852DCAC587 for ; Tue, 9 Sep 2025 13:59:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0504A8E0007; Tue, 9 Sep 2025 09:59:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 026B38E0003; Tue, 9 Sep 2025 09:59:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EA5C28E0007; Tue, 9 Sep 2025 09:59:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id DA7988E0003 for ; Tue, 9 Sep 2025 09:59:54 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 8A2F0B9F8A for ; Tue, 9 Sep 2025 13:59:54 +0000 (UTC) X-FDA: 83869870308.28.70DF5C7 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf08.hostedemail.com (Postfix) with ESMTP id BF960160005 for ; Tue, 9 Sep 2025 13:59:52 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf08.hostedemail.com: domain of kevin.brodsky@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=kevin.brodsky@arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1757426393; a=rsa-sha256; cv=none; b=w9tv0zo9Y8w/xEynVgwUBC+vukdB0F2tWmcCQk00Rt6RbZPgLHxJtIDgLiBxgahq4aJ4hd SSo272LlHjMWuo7cXwS9luPanSpnD0/Ti7uSSZSCdfaW6eWQ85KtjB6AiHssSJO8J48JY7 dgI6L7W52p4pJMM7RPVWybP1l8VU2hs= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf08.hostedemail.com: domain of kevin.brodsky@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=kevin.brodsky@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1757426393; 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; bh=me/PYrVLsmNCRPmt3YLLhQOu31Dt2HxN8RzThRmkvck=; b=2AbTe/3ow0RgU+KfrKakAQ8DWga9qf+unnZpC8LnbDAixcurdCas6fj8opEpkLdu5Q4IKu +jCZPdZio834RObMSdlWl7NfYnhvLwPdsaH7kf4fPN/VXvkFc+GinvOyldH2/U394tOOfY s13rE132PrZX/SflWPccXl2wdV4tPdY= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5E9261424; Tue, 9 Sep 2025 06:59:43 -0700 (PDT) Received: from [10.44.160.77] (e126510-lin.lund.arm.com [10.44.160.77]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4CF773F66E; Tue, 9 Sep 2025 06:59:44 -0700 (PDT) Message-ID: <203c84db-1a58-42f0-a79b-35104d79e964@arm.com> Date: Tue, 9 Sep 2025 15:59:41 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/7] Nesting support for lazy MMU mode To: David Hildenbrand , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Alexander Gordeev , Andreas Larsson , Boris Ostrovsky , Borislav Petkov , Catalin Marinas , Christophe Leroy , Dave Hansen , "David S. Miller" , "H. Peter Anvin" , Ingo Molnar , Jann Horn , Juergen Gross , "Liam R. Howlett" , Lorenzo Stoakes , Madhavan Srinivasan , Michael Ellerman , Michal Hocko , Mike Rapoport , Nicholas Piggin , Peter Zijlstra , Ryan Roberts , Suren Baghdasaryan , Thomas Gleixner , Vlastimil Babka , Will Deacon , Yeoreum Yun , linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, xen-devel@lists.xenproject.org References: <20250908073931.4159362-1-kevin.brodsky@arm.com> <20250908191602.61160a7990b9ea418de758c7@linux-foundation.org> Content-Language: en-GB From: Kevin Brodsky In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: BF960160005 X-Stat-Signature: xp5brrreb5e7fxtnxmdndnie9c9do6d9 X-Rspam-User: X-HE-Tag: 1757426392-659082 X-HE-Meta: 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 ysMLRBYu eCgpZWr9HcAXbEzvLuc2wn3VmTV3S0WeC1Tv6YzjPsysLVSoxqueI05QiepNf7gYlrwflIjSdFTWtSoNvOA0MFoDLKk7cQ1NgM1vCsVoFZdc7ViTT9C9j6XqGBw7lDhMys0DQWCCV54HTGVhWNCAW4zfAiHEZDTkNZIKXir4yMPGO1ifq5imKq2pD70yKLl6og7IhH5mxkTNWQrouL5duTAIqxjBP9lf3PBCZJnSYyfEVEJJeofEDgxtkA5eqC5IF46In 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 09/09/2025 11:21, David Hildenbrand wrote: > On 09.09.25 04:16, Andrew Morton wrote: >> On Mon,  8 Sep 2025 08:39:24 +0100 Kevin Brodsky >> wrote: >> >>> The main change enabling nesting is patch 2, following the approach >>> suggested by Catalin Marinas [4]: have enter() return some state and >>> the matching leave() take that state. >> >> This is so totally the correct way.  Thanks. > > Staring at this, I wonder if we could alternatively handle it like > pagefault_disable()/pagefault_enable(), having something like > current->lazy_mmu_enabled. > > We wouldn't have to worry about preemption in that case I guess > (unless the arch has special requirements). > > Not sure if that was already discussed, just a thought.  That's an interesting point, I think I've addressed it in reply to patch 2 [1]. - Kevin [1] https://lore.kernel.org/all/47ee1df7-1602-4200-af94-475f84ca8d80@arm.com/