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 81436C61DBD for ; Fri, 28 Aug 2026 06:13:14 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wzpp4-0001Ue-Hs; Fri, 28 Aug 2026 02:12:18 -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 1wzpoz-0001BT-Ef; Fri, 28 Aug 2026 02:12:13 -0400 Received: from tor.source.kernel.org ([172.105.4.254]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wzpox-0001Xv-4y; Fri, 28 Aug 2026 02:12:13 -0400 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 5B94260A8B; Fri, 28 Aug 2026 06:12:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CD3C81F000E9; Fri, 28 Aug 2026 06:12:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787897529; bh=UFPElJnUXqTd55dttDAu3yb9ihVgM0+HLoF3lSR03Mw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=bop4OAJQdY3iHZkooq/5ENSEl+5/Le4U19me6LSPpvx+RCrgUflgSAVh+h34eXSMi Jq31knm3ru32hWvbswwMd5DL2lfVsdP9Aggua7aeNIFzp9Tvx2EDMnGgfEFjZbKMte zxZAOgD0pz+tqHD/Ngp/takW86xzbTq/HtpbB12gLpp1lrEndV+mjMO4vOPpUHCwQa YhoIAWW2GZ3WfjuxypG3JfPDmXHXQnRm+ErGEMRG3pxYN4LRKOs2HyzH5rEbEdcNT8 4N3LvIIEv6TQj8o6Nw+Y7RHTwCRJB2GCiQOwVap2ss/ChwtDPFaGN9qrTc67XEsXoy IS+6n8Y9huzmQ== Message-ID: <38424bc3-c8d7-4167-9b5d-b139becea55e@kernel.org> Date: Fri, 28 Aug 2026 15:12:06 +0900 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 06/12] hw/block: reject a zoned device whose write pointers are unaddressable To: Niklas Cassel , Stefan Hajnoczi , John Snow , "Denis V. Lunev" , Kevin Wolf , Hanna Reitz , "Michael S. Tsirkin" Cc: Sam Li , qemu-block@nongnu.org, qemu-devel@nongnu.org References: <20260825205748.679968-1-cassel@kernel.org> <20260825205748.679968-7-cassel@kernel.org> Content-Language: en-US From: Damien Le Moal Organization: Western Digital Research In-Reply-To: <20260825205748.679968-7-cassel@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=172.105.4.254; envelope-from=dlemoal@kernel.org; helo=tor.source.kernel.org X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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: 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 On 8/26/26 05:57, 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=512 > leaves a write pointer that is a multiple of 512, and attaching the same > device with logical_block_size=4096 makes that pointer unaddressable. > > 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. > > 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: > > $ qemu-io --image-opts -n driver=host_device,filename=/dev/nullb0 \ > -c "zap -p 0x20000000 0x200" -c "zrp 0x20000000 1" > start: 0x100000, len 0x80000, cap 0x80000, wptr 0x100001, zcond:2 > > Attaching that disk with logical_block_size=4096 handed the guest a zone > it could not write to. > > 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. > > 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. > > 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(+) > > diff --git a/hw/block/block.c b/hw/block/block.c > index 1c3135843d..b908e0ef64 100644 > --- a/hw/block/block.c > +++ b/hw/block/block.c > @@ -208,6 +208,52 @@ uint32_t blkconf_zone_write_granularity(BlockConf *conf) > return MAX(bs->bl.write_granularity, conf->logical_block_size); > } > > +bool blkconf_zoned(BlockConf *conf, Error **errp) > +{ > + BlockDriverState *bs = blk_bs(conf->blk); > + uint32_t wg; > + > + if (bs->bl.zoned == BLK_Z_NONE) { This test and the name of the function are making things very confusing... Maybe rename the function: blkconf_zoned_alignement_ok() or something like that? > + return true; > + } > + > + wg = blkconf_zone_write_granularity(conf); > + > + if (!QEMU_IS_ALIGNED(bs->bl.zone_size, wg)) { > + error_setg(errp, "zone size %" PRIu64 " is not a multiple of the zone " > + "write granularity %" PRIu32, bs->bl.zone_size, wg); > + return false; > + } > + > + /* > + * A write pointer that is not a multiple of the write granularity does not > + * fall on a logical block boundary, so the guest can neither read nor write > + * at it and the zone can only be recovered by resetting it. A backend that > + * records its write pointers, rather than reading them back from a device, > + * can hand us such a pointer when the zones were written while the device > + * was configured with a smaller logical block size. > + */ > + for (uint32_t i = 0; i < bs->bl.nr_zones; i++) { > + uint64_t wp = bs->wps->wp[i]; > + > + if (BDRV_ZT_IS_CONV(wp)) { > + continue; > + } > + > + if (!QEMU_IS_ALIGNED(wp, wg)) { > + error_setg(errp, "write pointer 0x%" PRIx64 " of zone %" PRIu32 > + " is not a multiple of the zone write granularity %" > + PRIu32, wp, i, wg); > + error_append_hint(errp, "The zones were written with a smaller " > + "logical_block_size. Reset them, or keep using " > + "the smaller size.\n"); > + return false; > + } > + } > + > + return true; > +} > + > bool blkconf_apply_backend_options(BlockConf *conf, bool readonly, > bool resizable, Error **errp) > { > diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c > index 7977f4abe5..61f7b3cdc1 100644 > --- a/hw/block/virtio-blk.c > +++ b/hw/block/virtio-blk.c > @@ -1821,6 +1821,10 @@ static void virtio_blk_device_realize(DeviceState *dev, Error **errp) > return; > } > > + if (!blkconf_zoned(&conf->conf, errp)) { > + return; > + } > + > bs = blk_bs(conf->conf.blk); > if (bs->bl.zoned != BLK_Z_NONE) { > virtio_add_feature(&s->host_features, VIRTIO_BLK_F_ZONED); > diff --git a/include/hw/block/block.h b/include/hw/block/block.h > index f98525c01a..3c96de3222 100644 > --- a/include/hw/block/block.h > +++ b/include/hw/block/block.h > @@ -122,6 +122,7 @@ bool blkconf_blocksizes(BlockConf *conf, Error **errp); > * value to its guest and validate requests against it. > */ > uint32_t blkconf_zone_write_granularity(BlockConf *conf); > +bool blkconf_zoned(BlockConf *conf, Error **errp); > bool blkconf_apply_backend_options(BlockConf *conf, bool readonly, > bool resizable, Error **errp); > -- Damien Le Moal Western Digital Research