72 lines
2.7 KiB
ReStructuredText
72 lines
2.7 KiB
ReStructuredText
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.. _OpenRISC-System-emulator:
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OpenRISC System emulator
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~~~~~~~~~~~~~~~~~~~~~~~~
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QEMU can emulate 32-bit OpenRISC CPUs using the ``qemu-system-or1k`` executable.
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OpenRISC CPUs are generally built into "system-on-chip" (SoC) designs that run
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on FPGAs. These SoCs are based on the same core architecture as the or1ksim
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(the original OpenRISC instruction level simulator) which QEMU supports. For
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this reason QEMU does not need to support many different boards to support the
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OpenRISC hardware ecosystem.
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The OpenRISC CPU supported by QEMU is the ``or1200``, it supports an MMU and can
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run linux.
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Choosing a board model
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======================
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For QEMU's OpenRISC system emulation, you must specify which board model you
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want to use with the ``-M`` or ``--machine`` option; the default machine is
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``or1k-sim``.
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If you intend to boot Linux, it is possible to have a single kernel image that
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will boot on any of the QEMU machines. To do this one would compile all required
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drivers into the kernel. This is possible because QEMU will create a device tree
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structure that describes the QEMU machine and pass a pointer to the structure to
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the kernel. The kernel can then use this to configure itself for the machine.
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However, typically users will have specific firmware images for a specific machine.
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If you already have a system image or a kernel that works on hardware and you
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want to boot with QEMU, check whether QEMU lists that machine in its ``-machine
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help`` output. If it is listed, then you can probably use that board model. If
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it is not listed, then unfortunately your image will almost certainly not boot
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on QEMU. (You might be able to extract the filesystem and use that with a
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different kernel which boots on a system that QEMU does emulate.)
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If you don't care about reproducing the idiosyncrasies of a particular
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bit of hardware, such as small amount of RAM, no PCI or other hard disk, etc.,
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and just want to run Linux, the best option is to use the ``virt`` board. This
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is a platform which doesn't correspond to any real hardware and is designed for
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use in virtual machines. You'll need to compile Linux with a suitable
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configuration for running on the ``virt`` board. ``virt`` supports PCI, virtio
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and large amounts of RAM.
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Board-specific documentation
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============================
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..
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This table of contents should be kept sorted alphabetically
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by the title text of each file, which isn't the same ordering
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as an alphabetical sort by filename.
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.. toctree::
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:maxdepth: 1
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openrisc/or1k-sim
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openrisc/virt
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Emulated CPU architecture support
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=================================
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.. toctree::
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openrisc/emulation
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OpenRISC CPU features
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=====================
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.. toctree::
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openrisc/cpu-features
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