91d3e2d429
Refactor the code and make it easier to read. It's useful for understanding the inflight APIs and how packed ring works. Update the RST because the packed ring patch has been merged to QEMU master and ring_packed parameter changes to packed. Signed-off-by: Jin Yu <jin.yu@intel.com> Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
66 lines
2.2 KiB
ReStructuredText
66 lines
2.2 KiB
ReStructuredText
.. SPDX-License-Identifier: BSD-3-Clause
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Copyright(c) 2010-2017 Intel Corporation.
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Vhost_blk Sample Application
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=============================
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The vhost_blk sample application implemented a simple block device,
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which used as the backend of Qemu vhost-user-blk device. Users can extend
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the exist example to use other type of block device(e.g. AIO) besides
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memory based block device. Similar with vhost-user-net device, the sample
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application used domain socket to communicate with Qemu, and the virtio
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ring (split or packed format) was processed by vhost_blk sample application.
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The sample application reuse lots codes from SPDK(Storage Performance
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Development Kit, https://github.com/spdk/spdk) vhost-user-blk target,
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for DPDK vhost library used in storage area, user can take SPDK as
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reference as well.
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Testing steps
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-------------
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This section shows the steps how to start a VM with the block device as
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fast data path for critical application.
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Compiling the Application
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-------------------------
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To compile the sample application see :doc:`compiling`.
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The application is located in the ``examples`` sub-directory.
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You will also need to build DPDK both on the host and inside the guest
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Start the vhost_blk example
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.. code-block:: console
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./vhost_blk -m 1024
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.. _vhost_blk_app_run_vm:
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Start the VM
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~~~~~~~~~~~~
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.. code-block:: console
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qemu-system-x86_64 -machine accel=kvm \
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-m $mem -object memory-backend-file,id=mem,size=$mem,\
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mem-path=/dev/hugepages,share=on -numa node,memdev=mem \
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-drive file=os.img,if=none,id=disk \
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-device ide-hd,drive=disk,bootindex=0 \
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-chardev socket,id=char0,reconnect=1,path=/tmp/vhost.socket \
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-device vhost-user-blk-pci,packed=on,chardev=char0,num-queues=1 \
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...
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.. note::
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You must check whether your Qemu can support "vhost-user-blk" or not,
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Qemu v4.0 or newer version is required.
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reconnect=1 means live recovery support that qemu can reconnect vhost_blk
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after we restart vhost_blk example.
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packed=on means the device support packed ring but need the guest kernel
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version >= 5.0.
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Now Qemu commit 9bb73502321d46f4d320fa17aa38201445783fc4 both support the
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vhost-blk reconnect and packed ring.
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