DOC: Usage guide for Virtio-blk blkrescan feature
This patch adds the steps required to use the newly introduced blkrescan feature for Virtio-blk device. Tracked-On: #3051 Signed-off-by: Vijay Dhanraj <vijay.dhanraj@intel.com>
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@ -795,6 +795,35 @@ To use the Virtio-blk device, use the following command:
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nohpet console=hvc0 no_timer_check ignore_loglevel \
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log_buf_len=16M consoleblank=0 tsc=reliable" vm1
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Virtio-blk also supports rescan feature. Virtio-blk rescan is helpful
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when the size/path of the Virtio-blk device's backing file (on the host)
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changes and the guest needs to refresh its internal data structures to
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pick up this change. Using rescan feature is simple, add Virtio-blk
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device with dummy backend using "**nodisk**" keyword instead of a backing
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file.
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To create a Virtio-blk device with dummy backend,
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use the following command:
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.. code-block:: bash
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./acrn-dm -A -m 1168M \
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-s 0:0,hostbridge \
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-s 1,virtio-blk,**nodisk** \
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-k bzImage -B "root=/dev/vda rw rootwait noxsave maxcpus=0 \
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nohpet console=hvc0 no_timer_check ignore_loglevel \
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log_buf_len=16M consoleblank=0 tsc=reliable" vm1
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After VM launch, user can replace the dummy backend file with the
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actual file using acrnctl "blkrescan" cmd as shown below,
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.. code-block:: bash
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acrnctl blkrescan vm1 1,actual_file.img
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Please refer to :ref:`acrnctl` for further details on
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``acrnctl blkrescan`` command.
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To verify the result, you should expect the user OS to boot
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successfully.
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@ -32,6 +32,7 @@ You can see the available ``acrnctl`` commands by running:
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suspend
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resume
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reset
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blkrescan
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Use acrnctl [cmd] help for details
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Here are some usage examples:
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@ -93,6 +94,27 @@ Use the ``stop`` command to stop one or more running VM:
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# acrnctl stop vm-yocto vm1-14:59:30 vm-android
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RESCAN BLOCK DEVICE
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===================
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Use the ``blkrescan`` command to trigger a rescan of
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virtio-blk device by guest VM, in order to revalidate and
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update the backend file.
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.. code-block:: none
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# acrnctl blkrescan vmname slot,newfilepath
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vmname: Name of VM with dummy backend file attached to virtio-blk device.
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slot: Slot number of the virtio-blk device.
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newfilepath: File path for the backend of virtio-blk device.
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acrnctl blkrescan vm1 6,actual_file.img
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.. note:: blkrescan is only supported when VM is launched with
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empty backend file (using **nodisk**) for virtio-blk device.
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Replacing a valid backend file is not supported and will
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result in error.
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.. _acrnd:
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acrnd
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