From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 654A13563D9; Thu, 22 Jan 2026 22:41:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769121692; cv=none; b=dzYujC4XDjqyHbAiN2i59B9jJiiONWbQnRHhVzrwnWgxZTijsxJrVWsWQcb0Hx8kN7x7qGySMZWl+CccGZNJGKHkvmFUeicWtGUZMZFQoZ2a2dTeJf8VTqLOiaWgbhxNYHWHPa8R+i6NX54J4HIb2k2kpbQA9XAy2Uiv/9QHCBI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769121692; c=relaxed/simple; bh=ltunTCCxLClZAqNMOmXb49EoyZfyf/+7jYjno2nXdHY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=kg4RuOqj2Mv15U3M8jz6+yMBQn5ZAh507tVIhLYBQh3MrqPQgyskzlvh6jrB3lTkiIgOa89DsqxMqTGajLm1Jf51SiZIFGTaRFrqJIDCG893gu3/8i1sgf4TZmuV3+Pr2Eap3maolfvTspZ6t1Idf+KIvBbToD9pmnuw0SaZmaw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JV+htoEF; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JV+htoEF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D5F92C116C6; Thu, 22 Jan 2026 22:41:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769121691; bh=ltunTCCxLClZAqNMOmXb49EoyZfyf/+7jYjno2nXdHY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=JV+htoEFB0wO2aziMKYdhq0dvY+C5OmmZw5YpFsknRRVCpqmW6JvCjDnS0gz6zY6P 5jDdjxYGB8V53GIu/3zWtFjDab+zbJlKJqlz5i/SvnKwVlkf8JgSx3In4EhCND6ZAT c4fwD8NFjUU9GSl8yL+3w4mCYGD3ACM0+L2CP2Yp1VU1eXg/w74xV6tEn6mRJK5EB1 0dZvMnKaKQxwYrMzV4yt7tVJ8TYXOk94DCBbHmF6KJalI2T7VYiL2OQzF/3RLMnayW 5k8sy46SJ2opItsi+qX9h+imOmMqpPVf3plrJBwb/Mx/OHG0gk/xJd0C5epIwvl5Wl rDC/A/c+btr1w== Message-ID: <4520e7b0-8218-404d-8ede-e62d95c50825@kernel.org> Date: Thu, 22 Jan 2026 23:41:24 +0100 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/8] mm/memory_hotplug: add APIs for explicit online type control To: Gregory Price Cc: linux-mm@kvack.org, linux-cxl@vger.kernel.org, nvdimm@lists.linux.dev, linux-kernel@vger.kernel.org, virtualization@lists.linux.dev, kernel-team@meta.com, dan.j.williams@intel.com, vishal.l.verma@intel.com, dave.jiang@intel.com, mst@redhat.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com, osalvador@suse.de, akpm@linux-foundation.org References: <20260114085201.3222597-1-gourry@gourry.net> <20260114085201.3222597-4-gourry@gourry.net> From: "David Hildenbrand (Red Hat)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit >> For dax we know that user space will define the policy. >> > > Actually this may not always be true. A driver spawning a dax on probe > might also end up selecting the policy... eventually... maybe... I might > be planning to add that glue between CXL and DAX so I can add some > config similar to the system-default policy to avoid systems with > multiple memory-devices being forced into the same policy > > (e.g. CXL memory device can online auto in ZONE_MOVABLE, but the other > device can have its own policy). > > There's a weird corner case for CXL auto-regions (BIOS configured > everything but left the memory EFI_MEMORY_SP - so comes up as DAX). > I'm trying to keep those systems working the same as they have been > while the userland policy stuff catches up. Early CXL patterns are :[ Right, but I don't want any other OOT kernel module to be able to make use of add_memory_driver_managed() to do arbitrary things, because we don't know if it's really user space setting the policy for that memory then. So either restrict add_memory_driver_managed() to kmem+virtio_mem completely, or add another variant that will be kmem-only (or however that dax/cxl module is called). -- Cheers David