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 125641DE887; Tue, 27 Jan 2026 21:34:32 +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=1769549673; cv=none; b=BejiWvRdA3EGolrRt0qD1ijIP6u1O0mtb9XIwTB+Nyism7YKKE38B2OWhbgX3WMfJloZuqF6yYhV6/jlp8GpA1bt1fxBgRxqTWBj79DKBMVuf6ofyThvT0s0aU/xLZR9eOvoenFyT2Eo01RyMyQTXT4v3bb5Wkxe+SJlzcryBb8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769549673; c=relaxed/simple; bh=bR9qRQiDPotvAWn2QIuk3A3vxmknksey0H/5pA0EgaU=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=bXpJh1ZTUVcelMli4IpSPVPCaPZ9uOofxPooLUbSb6nUhdQ1SVjiWnQpyPZYTBPkbMozLiUa7I6aosOTshdZGq9XCu5BkOFawqiSrJ5L4czbXVyBH6b/pE1VMDMLigxsRhg7R3vWlR76dU4RpH6La/FPjM+Juhrv8jOI11WyVAE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=DjTBNLHT; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="DjTBNLHT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 41A5FC116C6; Tue, 27 Jan 2026 21:34:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1769549672; bh=bR9qRQiDPotvAWn2QIuk3A3vxmknksey0H/5pA0EgaU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=DjTBNLHTNOC+jXRWsQ6HIWju6jaCg17tDZSayr8cblHACDU+z7Syip8Gie1ClWfDk YXi9aqZvE3iKKO+oV1rWm4swd+zSyWuVq6ApEnjlVtei99TwkJr9wfiAoy1CLgEKvE lAlqYtdgL6tUK0UDATd8mL/cp6frej8XW69FO5PU= Date: Tue, 27 Jan 2026 13:34:31 -0800 From: Andrew Morton 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, david@kernel.org, mst@redhat.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com, osalvador@suse.de Subject: Re: [PATCH] dax/kmem: add build config for protected dax memory blocks Message-Id: <20260127133431.671e4605eee807abe84f92f4@linux-foundation.org> In-Reply-To: <20260115024222.3486455-1-gourry@gourry.net> References: <20260114235022.3437787-6-gourry@gourry.net> <20260115024222.3486455-1-gourry@gourry.net> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 14 Jan 2026 21:42:22 -0500 Gregory Price wrote: > Since this protection may break userspace tools, it should > be an opt-in until those tools have time to update to the > new daxN.M/hotplug interface instead of memory blocks. > > --- a/drivers/dax/Kconfig > +++ b/drivers/dax/Kconfig > @@ -78,4 +78,22 @@ config DEV_DAX_KMEM > > Say N if unsure. > > +config DEV_DAX_KMEM_PROTECTED Users must rebuild and redeploy kernels after having updated a userspace tool. They won't thank us for this ;) Isn't there something we can do to make this feature backward-compatible?