7a1e049a70
Signed-off-by: Cédric Le Goater <clg@kaod.org> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Message-id: 20200602135050.593692-1-clg@kaod.org Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
98 lines
3.6 KiB
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98 lines
3.6 KiB
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.. _ARM-System-emulator:
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Arm System emulator
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-------------------
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QEMU can emulate both 32-bit and 64-bit Arm CPUs. Use the
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``qemu-system-aarch64`` executable to simulate a 64-bit Arm machine.
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You can use either ``qemu-system-arm`` or ``qemu-system-aarch64``
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to simulate a 32-bit Arm machine: in general, command lines that
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work for ``qemu-system-arm`` will behave the same when used with
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``qemu-system-aarch64``.
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QEMU has generally good support for Arm guests. It has support for
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nearly fifty different machines. The reason we support so many is that
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Arm hardware is much more widely varying than x86 hardware. Arm CPUs
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are generally built into "system-on-chip" (SoC) designs created by
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many different companies with different devices, and these SoCs are
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then built into machines which can vary still further even if they use
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the same SoC. Even with fifty boards QEMU does not cover more than a
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small fraction of the Arm hardware ecosystem.
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The situation for 64-bit Arm is fairly similar, except that we don't
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implement so many different machines.
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As well as the more common "A-profile" CPUs (which have MMUs and will
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run Linux) QEMU also supports "M-profile" CPUs such as the Cortex-M0,
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Cortex-M4 and Cortex-M33 (which are microcontrollers used in very
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embedded boards). For most boards the CPU type is fixed (matching what
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the hardware has), so typically you don't need to specify the CPU type
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by hand, except for special cases like the ``virt`` board.
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Choosing a board model
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======================
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For QEMU's Arm system emulation, you must specify which board
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model you want to use with the ``-M`` or ``--machine`` option;
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there is no default.
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Because Arm systems differ so much and in fundamental ways, typically
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operating system or firmware images intended to run on one machine
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will not run at all on any other. This is often surprising for new
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users who are used to the x86 world where every system looks like a
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standard PC. (Once the kernel has booted, most userspace software
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cares much less about the detail of the hardware.)
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If you already have a system image or a kernel that works on hardware
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and you want to boot with QEMU, check whether QEMU lists that machine
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in its ``-machine help`` output. If it is listed, then you can probably
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use that board model. If it is not listed, then unfortunately your image
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will almost certainly not boot on QEMU. (You might be able to
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extract the filesystem and use that with a different kernel which
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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
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disk, etc., and just want to run Linux, the best option is to use the
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``virt`` board. This is a platform which doesn't correspond to any
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real hardware and is designed for use in virtual machines. You'll
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need to compile Linux with a suitable configuration for running on
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the ``virt`` board. ``virt`` supports PCI, virtio, recent CPUs and
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large amounts of RAM. It also supports 64-bit CPUs.
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Board-specific documentation
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============================
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Unfortunately many of the Arm boards QEMU supports are currently
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undocumented; you can get a complete list by running
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``qemu-system-aarch64 --machine help``.
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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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arm/integratorcp
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arm/mps2
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arm/musca
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arm/realview
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arm/versatile
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arm/vexpress
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arm/aspeed
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arm/musicpal
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arm/nseries
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arm/orangepi
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arm/palm
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arm/xscale
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arm/sx1
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arm/stellaris
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Arm CPU features
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================
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.. toctree::
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arm/cpu-features
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