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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 717F3C47DD9 for ; Wed, 28 Feb 2024 06:45:14 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rfDfi-0003w4-Ag; Wed, 28 Feb 2024 01:44:06 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rfDfc-0003vU-B6 for qemu-devel@nongnu.org; Wed, 28 Feb 2024 01:44:01 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rfDfa-0002bh-3C for qemu-devel@nongnu.org; Wed, 28 Feb 2024 01:44:00 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1709102636; h=from:from: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=HGhSgZzOcIS0Vq2Ve5J2xQ8L9ZGjTGdVOSxvjMT6W2Y=; b=UIl8ivN1WOC2QS0z/77sBLNx6yDTHZiKlbvUNQnH+Sx3TmZk5vGbUdEDu8BP+2tjDf9wC8 LFOqzV35BABhkiJIWwvTh4JlPzOgzKCpDb7VsWyxFVhFjEu7XEoustiEDMpw92RkXi9iiN s6VAsSC6YgqQ7q0YWhsNLYiEuRMj7h4= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-596-MCjvOK-rMIiQr8xYFkL07Q-1; Wed, 28 Feb 2024 01:43:53 -0500 X-MC-Unique: MCjvOK-rMIiQr8xYFkL07Q-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D581E85A58C; Wed, 28 Feb 2024 06:43:52 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.193.4]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 542C61BDB1; Wed, 28 Feb 2024 06:43:52 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 2599E21E66F9; Wed, 28 Feb 2024 07:43:51 +0100 (CET) From: Markus Armbruster To: Yong Huang Cc: qemu-devel@nongnu.org, Kevin Wolf , Hanna Reitz , Eric Blake Subject: Re: [PATCH] qapi: Craft the BlockdevCreateOptionsLUKS comment In-Reply-To: (Yong Huang's message of "Wed, 21 Feb 2024 16:49:57 +0800") References: <91c52e03e46ff0a96559b4e7d66ded582b2ec4e1.1708486450.git.yong.huang@smartx.com> <874je22u83.fsf@pond.sub.org> <875xyiz0ho.fsf@pond.sub.org> Date: Wed, 28 Feb 2024 07:43:51 +0100 Message-ID: <87v8693x7c.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.5 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.088, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Yong Huang writes: > On Wed, Feb 21, 2024 at 4:26=E2=80=AFPM Markus Armbruster wrote: > >> Yong Huang writes: >> >> > On Wed, Feb 21, 2024 at 2:43=E2=80=AFPM Markus Armbruster >> wrote: >> > >> >> Hyman Huang writes: >> >> >> >> > Add comment in detail for commit 433957bb7f (qapi: >> >> > Make parameter 'file' optional for >> >> > BlockdevCreateOptionsLUKS). >> >> > >> >> > Signed-off-by: Hyman Huang >> >> > --- >> >> > qapi/block-core.json | 20 +++++++++++++++++++- >> >> > 1 file changed, 19 insertions(+), 1 deletion(-) >> >> > >> >> > diff --git a/qapi/block-core.json b/qapi/block-core.json >> >> > index ab5a93a966..42b0840d43 100644 >> >> > --- a/qapi/block-core.json >> >> > +++ b/qapi/block-core.json >> >> > @@ -4973,7 +4973,25 @@ >> >> > ## >> >> > # @BlockdevCreateOptionsLUKS: >> >> > # >> >> > -# Driver specific image creation options for LUKS. >> >> > +# Driver specific image creation options for LUKS. Note that >> >> > +# @file is required if @preallocation is specified and equals >> >> > +# PREALLOC_MODE_ON. The following three scenarios determine how >> >> > +# creation logic behaves when @preallocation is either equal to >> >> > +# PREALLOC_MODE_OFF or is not given: >> >> > +# >> >> > +# 1) When @file is given only, format the block device referenced >> >> > +# by @file as the LUKS specification and trunk it to the @size. >> >> >> >> Do you mean "truncate it to @size"? >> >> >> > Yes, :( sorry for the spelling mistake. >> >> Writing good documentation in a second language is *hard*. All we can >> reasonably expect from contributors to try their best. And then we >> improve the text together in review. Just like we do for code :) >> >> >> > +# In this case, the @size should reflect amount of space made >> >> > +# available to the guest, so the trunk size must take account >> >> > +# of that which will be used by the crypto header. >> >> > +# >> >> > +# 2) When @header is given only, just format the block device >> >> > +# referenced by @header as the LUKS specification. >> >> > +# >> >> > +# 3) When both @file and @header are given, block device >> >> > +# referenced by @file should be trunked to @size, and block >> >> > +# device referenced by @header should be formatted as the LUKS >> >> > +# specification. >> >> > # >> >> > # @file: Node to create the image format on, mandatory except when >> >> > # 'preallocation' is not requested >> >> >> >> Let's see whether I understand. >> >> >> >> blockdev-create with "driver": "luks" can work in three different way= s: >> >> >> >> 1. Create an image with a LUKS header >> >> >> >> 2. Create just a detached LUKS header >> >> >> >> 3. Create an image and a detached LUKS header >> >> >> >> Correct? >> >> >> > >> > Yes >> > >> > >> >> @file and @header are BlockdevRef, which means they refer to existing >> >> images with arbitrary driver. Could be "file", "qcow2", or anything. >> >> >> >> Correct? >> >> >> > Yes >> > >> > >> >> >> >> To get 1., specify @file, but not @header. >> >> >> >> To get 2., specify @header, but not @file. >> >> >> >> To get 3., specify both. >> >> >> >> Specifying neither is an error. >> >> >> >> Correct? >> >> >> > >> > Yes >> > >> > >> >> In any case, @size is the logical size of the image (how much data it >> >> can hold). >> >> >> > >> > Yes >> > >> > >> >> >> >> With 1., the actual image size is a bit larger due to the LUKS header. >> >> The @file image is resized to that size: if it's shorter, it's grown,= if >> >> it's longer, it's truncated. >> >> >> > >> > Yes >> > >> > >> >> With 2., @size is merely recorded in the detached LUKS header. >> >> >> > >> > In LUKS1 specification, payload data size is not contained in the head= er, >> > so in this case, @size is not recorded in the detached LUKS header. >> > The creation logic just does the LUKS header formatting only. >> >> Is @size unused then? >> > > IIUC, yes. Creation logic will ignore the @size. See the following code > in function block_crypto_co_create_luks: > > if (luks_opts->header) { > /* LUKS volume with detached header */ > hdr_bs =3D bdrv_co_open_blockdev_ref(luks_opts->header, errp); > if (hdr_bs =3D=3D NULL) { > return -EIO; > } > > cflags |=3D QCRYPTO_BLOCK_CREATE_DETACHED; > > /* Format the LUKS header node, here just ignore the size > * and passed zero to block_crypto_co_create_generic */ > ret =3D block_crypto_co_create_generic(hdr_bs, 0, &create_opts, > PREALLOC_MODE_OFF, cflags, e= rrp); > if (ret < 0) { > goto fail; > } > > /* Format the LUKS payload node */ > if (luks_opts->file) { > ret =3D block_crypto_co_format_luks_payload(luks_opts, errp); > if (ret < 0) { > goto fail; > } > } @size is a required argument, but silently ignored when @header is present and @file is absent (2. Create just a detached LUKS header). Feels awkward. Should @size be optional, absent when and only when @header is present and @file is absent? Kevin or Hanna, got an opinion? >> >> With 3., @size is recorded in the detached LUKS header, and the @file >> >> image is resized as with 1. >> >> >> > >> > Same reason as above, @size is not recorded and @file image is >> > resized to @size exactly. >> > >> > >> >> >> >> Correct? >> >> >> >> >> > Thanks for the comment, >> > >> > Yong >> >>