77 lines
2.6 KiB
ReStructuredText
77 lines
2.6 KiB
ReStructuredText
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.. _random_virtualization:
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Random device virtualization
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############################
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The virtual random device virtio-rnd provides a virtual hardware random
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source for UOS, based on virtio user mode framework. It simulates a PCI
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device based on virtio specification.
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Architecture
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************
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:numref:`rand-virt-arch` shows the Random Device Virtualization Architecture in ACRN.
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The green components are parts of the ACRN solution while the dark
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components are parts of Linux software or third party tools.
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virtio-rnd is implemented as a virtio legacy device in the ACRN device
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model (DM), and is registered as a PCI virtio device to the guest OS
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(UOS). Tools such as :command:`od` (dump a file in octal or other format) can
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be used to read random values from ``/dev/random``. This device file in
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UOS is bound with the frontend virtio-rng driver. (The guest kernel must
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be built with ``CONFIG_HW_RANDOM_VIRTIO=y``). The backend
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virtio-rnd reads the HW random value from ``/dev/random`` in SOS and sends
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them to frontend.
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.. figure:: images/rand-virt.png
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:align: center
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:name: rand-virt-arch
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Random Device Virtualization in ACRN
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How to Use
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**********
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Add a pci slot to the device model acrn-dm command line, for example::
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-s <slot_number>,virtio-rnd
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Check if the frontend virtio_rng driver is available in UOS:
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.. code-block:: console
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# cat /sys/class/misc/hw_random/rng_available
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virtio_rng.0
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Check if frontend virtio_rng is currently connected to ``/dev/random``:
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.. code-block:: console
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# cat /sys/class/misc/hw_random/rng_current
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virtio_rng.0
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Read random values:
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.. code-block:: console
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# od /dev/random
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0000000 007265 175751 147323 164223 060601 057377 027072 106352
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0000020 040765 045645 155773 111724 037572 152033 036001 056073
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0000040 057164 065021 024005 031500 156630 026635 022440 000127
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0000060 115071 046756 071656 106721 161340 106726 175275 072403
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0000100 011265 000420 061137 103723 001107 006430 061151 132766
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0000120 166216 015074 100505 015473 057324 102727 005126 051731
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0000140 003727 071115 167622 071407 120301 002616 047451 120733
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0000160 174117 133164 161231 035076 013700 164114 031627 001202
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0000200 011467 055650 016365 140074 060277 150601 043610 006403
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0000220 016170 071666 065540 026615 055073 162363 012002 112371
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0000240 000767 157121 125007 141671 000327 173741 056415 155463
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0000260 105504 066453 152754 136314 175213 063541 001420 053025
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0000300 047631 167425 044125 063176 171334 177234 050063 031640
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...
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.. note:: HW randomness is a precious resource of the system. The
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:command:`od` command will block and wait until there is randomness
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available.
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