From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qv1-f53.google.com (mail-qv1-f53.google.com [209.85.219.53]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D2A1B3264E2 for ; Thu, 13 Aug 2026 01:21:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.53 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786584075; cv=none; b=J/+leFF6fisD/WG+Oy1wtlgNGzDCiWm/gm1Jt+qqdtOmd7aZy8qLlbg7FvZteAPZAumGQnNasfy8ZzccsIRsWp3JrLq/+NvlJZOKr1AJ8IF7uZn2NgU+87NjN1zZPy3n0iYJjoio0IqHFYAAjsJg+DMtF0KNoctenPAPVwUwLG4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786584075; c=relaxed/simple; bh=jQAWRVENXd5JGHsxo/hf6vUttuV6ujE/QtYCehIVHRI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=FkZ/Til3b2tLuqTIuWF55sHJfsBZXOil1JIR6Ym3ev1+54+x7R6o6CbbaTp+awjn5CWXYHPzMWa7FwXweZMWXGdtjHAoCIr8u78GGDowQZY+zZXsN0ElVS7kMU3nCdnMb0qKEdg7j5uT66xbFQdOlmGoy4D/i9YcYux4cVtvVF8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=gourry.net; spf=pass smtp.mailfrom=gourry.net; dkim=pass (2048-bit key) header.d=gourry.net header.i=@gourry.net header.b=gV8Mq8xE; arc=none smtp.client-ip=209.85.219.53 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=gourry.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gourry.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gourry.net header.i=@gourry.net header.b="gV8Mq8xE" Received: by mail-qv1-f53.google.com with SMTP id 6a1803df08f44-9030f8ea3b3so1893346d6.1 for ; Wed, 12 Aug 2026 18:21:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gourry.net; s=google; t=1786584071; x=1787188871; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=ZGIPGO62vUWJJtnlWOV7HnIzQD6+wbjwlpycp53S1ew=; b=gV8Mq8xEA4vtp2rDR+jnsK6TSSY301yKIdCVoD89t2x3h9Hgh1rrBdXjPL+CXFnKeT SgVmxK9YhwfBk26NKuanp3J6BqnN7/USTpDab1KXu05gblpMHZZhHLaHX6OYZjrkSTT+ ndMAlJK/eFZotlpBWs/cl17UYJG9pm8sN7oSr2GxLXNHrirOvdufd5pCS61GGlFgjQET UblzbhY28gXamsNJPH9B9mCtMjh0uO2f2nXQy8B2vIpvJJnTFTdLMwOELMREAc5ZnPHV bljYuNumM7lTPeweZ05hCOaUTdzG6R7ZVXB7nWY2NU3i4BPv37QoHQw7aN/CUrDZSC0J p/0Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786584071; x=1787188871; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=ZGIPGO62vUWJJtnlWOV7HnIzQD6+wbjwlpycp53S1ew=; b=CKmbz6eZUHWDFhC8ryHYc5mDf1GrFaw9wJ7Wl3fYbYqd5YYTJ9fRs3N/Ao7d5NZn0g MO7BGihkk1bn00R2zSx9UgByWFC2M0bF+N7MGe0YG+5ggJMMYkYgpqVk2GjPz+CmZ3hd QfGFNpQyJHSVCNcLBEajqcy8xP09il63BFkpf4gR6vKBgrohV7xqsIc9p1ucAjcZuVbP N42rQmvygUb41wZRJIlgbk8Kz8CCCfV0QEusQRP6Uyfhk+vnRi2nx/md/MIoj4SKfNSv F/TPTzMQK///+GdJKUdXmJIyS5o88g4TNDuadaQruTIIexg9H5cwi8Jxq4pUJ7jSsDWm Vevg== X-Forwarded-Encrypted: i=1; AHgh+RoBJAi+V9Sje71Aat9YxtMSMfeTXKDR8QCkjW9poQKNLw9R0pbYJ3VhdwKg4iOrJnT2q9E=@vger.kernel.org X-Gm-Message-State: AOJu0Yx6XDFtFOCC0YiKapSrjF0QJxLy9b6BZ3kYqOl9JygkVABhDyzu //D9Nn3yhZR/4AnFqMlQvxCALABtzaHPlr76lgM1lbTWsmhfSYmYoBjjbSYIhlqjaK4= X-Gm-Gg: AR+sD135r3G/EIxMjZDddQ4lDIx0eGJDvli//BV4ymC5HFyduz6LDycQr29IgP6s13S 1kPLhrApnHPNA2qexQFqzPO83OiOLvl8O6RnTU8F538aus1qEHm+3UEKh0KaoJP/UJmGrPKWPwB 2QGe4dZCdp/BQZGYhgHdpJBFHVZa7sxWqmEuydugRUXJc1u6Jw5er4oJCZSnG242vdyTj3HnlDK ea2ruHXDDc4Sf205zwuzIxT09gBD1oUHlWBgQTDAY2MH4GAMNaR2hvqaUpjJnr8PCTJm0zPG6Vl ZAcLUBbq3ND2N8oZXQ6tac6AMNfbVRWHAI+UBnS95K5BA2gx6F5FIz9oRiibma/vCMbBSFojwEA fi5W8ufwp/dNUtous8fJHXWDzkOecBq6TDUm6Ic4T2vhzXq9zEKFGL4NWdhyZv/f0XXeTuiP2tY JKn8yXbFVLBKLzjXp7aBG0uZWk+emX0JeRZ7RwYdZKYev4k/M= X-Received: by 2002:a05:6214:500b:b0:8f0:d710:26ba with SMTP id 6a1803df08f44-90a80bb0b74mr17793966d6.31.1786584071577; Wed, 12 Aug 2026 18:21:11 -0700 (PDT) Received: from fedora ([2601:19e:8500:d3c0::28fe]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-90a8179e350sm4119856d6.6.2026.08.12.18.21.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Aug 2026 18:21:10 -0700 (PDT) Date: Wed, 12 Aug 2026 21:21:04 -0400 From: Gregory Price To: Pankaj Gupta Cc: linux-mm@kvack.org, Zhigang.Luo@amd.com, arun.george@samsung.com, balbirs@nvidia.com, brendan.jackman@linux.dev, yuzenghui@huawei.com, apopple@nvidia.com, alucerop@amd.com, matthew.brost@intel.com, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, corbet@lwn.net, skhan@linuxfoundation.org, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, djbw@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, alison.schofield@intel.com, osandov@osandov.com, jannh@google.com, pfalcato@suse.de, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, pbonzini@redhat.com, osalvador@suse.de, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, kasong@tencent.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, yury.norov@gmail.com, linux@rasmusvillemoes.dk, longman@redhat.com, ridong.chen@linux.dev, tj@kernel.org, mkoutny@suse.com, sj@kernel.org, jgg@ziepe.ca, jhubbard@nvidia.com, peterx@redhat.com, baolin.wang@linux.alibaba.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, lance.yang@linux.dev, usama.arif@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, roman.gushchin@linux.dev, muchun.song@linux.dev, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, driver-core@lists.linux.dev, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-debuggers@vger.kernel.org, linux-fsdevel@vger.kernel.org, kvm@vger.kernel.org, cgroups@vger.kernel.org, damon@lists.linux.dev, linux-kselftest@vger.kernel.org, kernel-team@meta.com, "Gupta, Pankaj" Subject: Re: [PATCH v5 00/36] Private Memory NUMA Nodes Message-ID: References: <20260720193431.3841992-1-gourry@gourry.net> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Aug 12, 2026 at 02:01:12PM +0200, Pankaj Gupta wrote: > > > > Bonus Configuration: HBM device memory tiering > > ============================================== > > echo 1 > dax0.0/private # make the node private > > echo 0 > dax0.0/adistance # highest tier > > echo 1 > dax0.0/reclaim # reclaim active > > echo 1 > dax0.0/demotion # may demote from the node > > echo 1 > dax0.0/user_numa # mbind() > > echo online_movable > dax0.0/state > > echo 1 > numa/demotion_enabled > > I am bit confused by the HBM device example being discovered as a DAX > device. Is it to > only to showcase the use-case? Or we see HBM device is actually > expected to be discovered as > DAX device with N_MEMORY_PRIVATE? > "actually expected to be" -> no. there's no requirement HBM be discovered and boudn to DAX, DAX is simply a convenient intermediary to memory-hotplug. This is at best a demonstration. A device driver could very well just call memory-hotplug directly, or its memory could be brought up as a private node via a boot paremeter (which I have sculpted for v7). The former is preferred, but there's a bit of a chicken/egg scenario for bootstrapping. Most of these UAPI extensions are going to be consolidated into a debugfs interface for testing purposes only in v7. I've been working on aggressive Linux Test Project test expansion to ensure there is no UAPI regressions. ~Gregory