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 B755D1ACED9; Tue, 27 May 2025 13:26:00 +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=1748352360; cv=none; b=GFiibJ5mRt7TznuVHMhPRjHha+GCio423Xs0XKVcDn7dzg2X26SKEPi13tcgqTvzz4tDA3Lcjif1Z+0q6IOr6cKtZuxWkDqLmfjow5gcfCFtv2JMUOCBNQHVi4jvTi1NYXiNm8qiOwbi7+VLnxKmYtWaf9CPUfQTPXa3Z1ERzQ0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748352360; c=relaxed/simple; bh=RJZrjlZXyF2IEyk45tZVLBAEfHaJeaF88xrgOYA4D9A=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=fwLsthoAyiX+WL15WbpElulBR/Qt8O7iS8kcuiYsqnDCQdx8DeD3rSEPBjeSQYkGJIogPwltrLXQIbrXTuFKxNxnlRpvKiOGhshpvDDNbxsoHSi8hc29cOTCiH3b7l497xaGvZYjpfIw3/pIwWqaQn5lSEOE/x+ID2dgXuzM9+U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fXuaWA2T; 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="fXuaWA2T" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EAF88C4CEE9; Tue, 27 May 2025 13:25:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1748352360; bh=RJZrjlZXyF2IEyk45tZVLBAEfHaJeaF88xrgOYA4D9A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=fXuaWA2TjqMjpqvK8uJbUl1dUHB8Dq7WIOcO4O8pSnnhGpYuXPQaQcs8SzLFZoh5Z 97P9pFajTEqwuagTGvgdRuKBDpbU7axVuFJA2CI36xHsGwRY877Ywstr6AwtLUT3Za PTF1mE2BUyUJHV+ihfNBVv5lPsPdsuLJfhNUcUNPsbK3FR8/V5ZzxYfEYfNlO8ZwPY +P7Obe+q5od1kiRvY8lBN6Jf4zVF9UwUe9hj7dj8mrXFa9bBmThgOPpb8rw+Jg1/ir MIDjN2mf0c9WyYVZENEbUU+Xr+dloN1i6diuYiQkopPpKAFCnxdPF+6DV1Khjili9Q 2+kgyLidpun3g== Date: Tue, 27 May 2025 16:25:53 +0300 From: Mike Rapoport To: Pasha Tatashin Cc: Ira Weiny , Michal Clapinski , Dan Williams , Vishal Verma , Dave Jiang , Jonathan Corbet , nvdimm@lists.linux.dev, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/1] libnvdimm/e820: Add a new parameter to configure many regions per e820 entry Message-ID: References: <20250417142525.78088-1-mclapinski@google.com> <6805a8382627f_18b6012946a@iweiny-mobl.notmuch> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Apr 21, 2025 at 10:55:25AM -0400, Pasha Tatashin wrote: > On Sun, Apr 20, 2025 at 10:06 PM Ira Weiny wrote: > > > > Michal Clapinski wrote: > > > Currently, the user has to specify each memory region to be used with > > > nvdimm via the memmap parameter. Due to the character limit of the > > > command line, this makes it impossible to have a lot of pmem devices. > > > This new parameter solves this issue by allowing users to divide > > > one e820 entry into many nvdimm regions. > > > > > > This change is needed for the hypervisor live update. VMs' memory will > > > be backed by those emulated pmem devices. To support various VM shapes > > > I want to create devdax devices at 1GB granularity similar to hugetlb. > > > > Why is it not sufficient to create a region out of a single memmap range > > and create multiple 1G dax devices within that single range? > > This method implies using the ndctl tool to create regions and convert > them to dax devices from userspace. This does not work for our use > case. We must have these 1 GB regions available during boot because we > do not want to lose memory for a devdax label. I.e., if fsdax is > created during boot (i.e. default pmem format), it does not have a > label. However, if it is created from userspace, we create a label > with partition properties, UUID, etc. Here, we need to use kernel Doesn't ndctl refuse to alter namespaces on "legacy" (i.e. memmap=) regions? > parameters to specify the properties of the pmem devices during boot > so they can persist across reboots without losing any memory to > labels. > > Pasha -- Sincerely yours, Mike.