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([112.44.202.248]) by smtp.gmail.com with ESMTPSA id q9-20020a63d609000000b004405c6eb962sm1232801pgg.4.2022.10.27.08.46.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Oct 2022 08:46:21 -0700 (PDT) From: Sam Li To: qemu-devel@nongnu.org Cc: Fam Zheng , Hanna Reitz , damien.lemoal@opensource.wdc.com, qemu-block@nongnu.org, stefanha@redhat.com, Markus Armbruster , hare@suse.de, Kevin Wolf , dmitry.fomichev@wdc.com, Eric Blake , Sam Li Subject: [PATCH v13 8/8] docs/zoned-storage: add zoned device documentation Date: Thu, 27 Oct 2022 23:45:04 +0800 Message-Id: <20221027154504.20684-9-faithilikerun@gmail.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221027154504.20684-1-faithilikerun@gmail.com> References: <20221027154504.20684-1-faithilikerun@gmail.com> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::629; envelope-from=faithilikerun@gmail.com; helo=mail-pl1-x629.google.com 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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, 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: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Qemu-devel" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Add the documentation about the zoned device support to virtio-blk emulation. Signed-off-by: Sam Li Reviewed-by: Stefan Hajnoczi Reviewed-by: Damien Le Moal Reviewed-by: Dmitry Fomichev --- docs/devel/zoned-storage.rst | 43 ++++++++++++++++++++++++++ docs/system/qemu-block-drivers.rst.inc | 6 ++++ 2 files changed, 49 insertions(+) create mode 100644 docs/devel/zoned-storage.rst diff --git a/docs/devel/zoned-storage.rst b/docs/devel/zoned-storage.rst new file mode 100644 index 0000000000..03e52efe2e --- /dev/null +++ b/docs/devel/zoned-storage.rst @@ -0,0 +1,43 @@ +============= +zoned-storage +============= + +Zoned Block Devices (ZBDs) divide the LBA space into block regions called zones +that are larger than the LBA size. They can only allow sequential writes, which +can reduce write amplification in SSDs, and potentially lead to higher +throughput and increased capacity. More details about ZBDs can be found at: + +https://zonedstorage.io/docs/introduction/zoned-storage + +1. Block layer APIs for zoned storage +------------------------------------- +QEMU block layer supports three zoned storage models: +- BLK_Z_HM: The host-managed zoned model only allows sequential writes access +to zones. It supports ZBD-specific I/O commands that can be used by a host to +manage the zones of a device. +- BLK_Z_HA: The host-aware zoned model allows random write operations in +zones, making it backward compatible with regular block devices. +- BLK_Z_NONE: The non-zoned model has no zones support. It includes both +regular and drive-managed ZBD devices. ZBD-specific I/O commands are not +supported. + +The block device information resides inside BlockDriverState. QEMU uses +BlockLimits struct(BlockDriverState::bl) that is continuously accessed by the +block layer while processing I/O requests. A BlockBackend has a root pointer to +a BlockDriverState graph(for example, raw format on top of file-posix). The +zoned storage information can be propagated from the leaf BlockDriverState all +the way up to the BlockBackend. If the zoned storage model in file-posix is +set to BLK_Z_HM, then block drivers will declare support for zoned host device. + +The block layer APIs support commands needed for zoned storage devices, +including report zones, four zone operations, and zone append. + +2. Emulating zoned storage controllers +-------------------------------------- +When the BlockBackend's BlockLimits model reports a zoned storage device, users +like the virtio-blk emulation or the qemu-io-cmds.c utility can use block layer +APIs for zoned storage emulation or testing. + +For example, to test zone_report on a null_blk device using qemu-io is: +$ path/to/qemu-io --image-opts -n driver=zoned_host_device,filename=/dev/nullb0 +-c "zrp offset nr_zones" diff --git a/docs/system/qemu-block-drivers.rst.inc b/docs/system/qemu-block-drivers.rst.inc index dfe5d2293d..0b97227fd9 100644 --- a/docs/system/qemu-block-drivers.rst.inc +++ b/docs/system/qemu-block-drivers.rst.inc @@ -430,6 +430,12 @@ Hard disks you may corrupt your host data (use the ``-snapshot`` command line option or modify the device permissions accordingly). +Zoned block devices + Zoned block devices can be passed through to the guest if the emulated storage + controller supports zoned storage. Use ``--blockdev zoned_host_device, + node-name=drive0,filename=/dev/nullb0`` to pass through ``/dev/nullb0`` + as ``drive0``. + Windows ^^^^^^^