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 lists1p.gnu.org (lists1p.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 6C581C79FB7 for ; Wed, 9 Sep 2026 18:35:16 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1x4N8C-0004sY-RJ; Wed, 09 Sep 2026 14:34:48 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1x4N8B-0004ro-HI for qemu-devel@nongnu.org; Wed, 09 Sep 2026 14:34:47 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1x4N89-0006OD-OE for qemu-devel@nongnu.org; Wed, 09 Sep 2026 14:34:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1788978884; 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: in-reply-to:in-reply-to:references:references; bh=yKBEDnilrgkpBOOrh+dbk3UgtghIabGDsl/Pvs4j0NA=; b=MlPrcpkg7CG/uE57cIr8LHqyFoeThz1WySjEQowimhI07a6EZ4SBzt5svwT0fNnU+kRcHR lZRYkP8psids0P1UAndEN15iutzznpSWcsYGr5MqMNA3ipB6hXO81Fhzooni1lyxCKPW4j 7krNXzRphIDEOfSLeLUU/HPAAtim3P4= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-451-sJbQ6i2mOiqQRvKZHAoumg-1; Wed, 09 Sep 2026 14:34:40 -0400 X-MC-Unique: sJbQ6i2mOiqQRvKZHAoumg-1 X-Mimecast-MFC-AGG-ID: sJbQ6i2mOiqQRvKZHAoumg_1788978879 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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 mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5A4AB1954193; Wed, 9 Sep 2026 18:34:39 +0000 (UTC) Received: from localhost (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 780D818004D4; Wed, 9 Sep 2026 18:34:38 +0000 (UTC) Date: Wed, 9 Sep 2026 14:34:37 -0400 From: Stefan Hajnoczi To: Niklas Cassel Cc: Kevin Wolf , John Snow , "Denis V. Lunev" , Hanna Reitz , "Michael S. Tsirkin" , Sam Li , Damien Le Moal , qemu-block@nongnu.org, qemu-devel@nongnu.org Subject: Re: [PATCH v4 06/12] hw/block: reject a zoned device whose write pointers are unaddressable Message-ID: <20260909183437.GE20134@fedora> References: <20260907110748.1868714-1-cassel@kernel.org> <20260907110748.1868714-7-cassel@kernel.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="/YfYVLxMu9XUzckv" Content-Disposition: inline In-Reply-To: <20260907110748.1868714-7-cassel@kernel.org> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.129.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H2=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development 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 --/YfYVLxMu9XUzckv Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Sep 07, 2026 at 01:07:41PM +0200, Niklas Cassel wrote: > The write pointers of a zoned device outlive any particular use of it, > whether the device keeps them itself or a backend records them, while the > logical block size is a property of the frontend and is chosen afresh > every time the device is attached. Nothing ties the two together. A zone > written while the device was configured with logical_block_size=3D512 > leaves a write pointer that is a multiple of 512, and attaching the same > device with logical_block_size=3D4096 makes that pointer unaddressable. >=20 > Such a pointer is not merely misaligned. The guest addresses the device > in logical blocks, and a zone report expresses the write pointer in 512 > byte sectors, so the guest is told about a position that does not fall on > a logical block boundary. It can neither read nor write there, and the > zone can only be recovered by resetting it. The reverse direction is > harmless: a pointer laid down with a larger logical block size is still a > multiple of a smaller one. >=20 > On a zoned null_blk device with a logical block size of 512, a 512 byte > append to a sequential zone leaves the write pointer half a logical block > into it: >=20 > $ qemu-io --image-opts -n driver=3Dhost_device,filename=3D/dev/nullb0 \ > -c "zap -p 0x20000000 0x200" -c "zrp 0x20000000 1" > start: 0x100000, len 0x80000, cap 0x80000, wptr 0x100001, zcond:2 >=20 > Attaching that disk with logical_block_size=3D4096 handed the guest a zone > it could not write to. >=20 > Check at realize time that the zone size and every write pointer of a > sequential zone are multiples of the write granularity that the device is > about to report, and refuse to start otherwise. The write pointers are > already held in memory by the driver, so this costs no I/O. >=20 > The check uses blkconf_zone_write_granularity(), the same value that a > frontend reports to its guest and validates requests against, so the > three cannot disagree. >=20 > Reviewed-by: Damien Le Moal > Signed-off-by: Niklas Cassel > --- > hw/block/block.c | 46 ++++++++++++++++++++++++++++++++++++++++ > hw/block/virtio-blk.c | 4 ++++ > include/hw/block/block.h | 1 + > 3 files changed, 51 insertions(+) Reviewed-by: Stefan Hajnoczi --/YfYVLxMu9XUzckv Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmqhpr0ACgkQnKSrs4Gr c8i5GQf9GRuQe4uIKY+PBDjNMFuevEATbGCDhyQplgBt6XHQu3k6yyV3Dx8wLxez 6TWoga1Sd53eKW0CSxU3Nh2RFOWXaNDRWgaGf6Snub6VriVtNw4yTsXbspUo6qAs wJMNeLINiVNgzR4S8MNM8m0imXUTLwdK4Mt2rBUHJXj9B4/0ntabVneO9xpDvV8/ L3it9qvVQVd3QdwXNejVcxEz3yXo9URbibj8f359NxMMXxBZgwp6mUGXFeBMmXiB EVgEQToOQVQvxuWYChR4vWKzYgHKSBhDfjwzRCjF5cWMk4Rs8iomHdezJ3wE2wWb Lv+6N8RPObMvWOP7zky/CeHJHMKhyw== =UxR4 -----END PGP SIGNATURE----- --/YfYVLxMu9XUzckv--