system/arm/virt.rst

4 The ``virt`` board is a platform which does not correspond to any
6 It is the recommended board type if you simply want to run
8 idiosyncrasies and limitations of a particular bit of real-world
14 to have the same behaviour as that of previous QEMU releases, so
16 ``virt-5.0`` machine type will behave like the ``virt`` machine from
17 the QEMU 5.0 release, and migration should work between ``virt-5.0``
18 of the 5.0 release and ``virt-5.0`` of the 5.1 release. Migration
19 is not guaranteed to work between different QEMU releases for
20 the non-versioned ``virt`` machine type.
27 - PCI/PCIe devices
28 - Flash memory
29 - Either one or two PL011 UARTs for the NonSecure World
30 - An RTC
31 - The fw_cfg device that allows a guest to obtain data from QEMU
32 - A PL061 GPIO controller
33 - An optional SMMUv3 IOMMU
34 - hotpluggable DIMMs
35 - hotpluggable NVDIMMs
36 - An MSI controller (GICv2M or ITS). GICv2M is selected by default along
37   with GICv2. ITS is selected by default with GICv3 (>= virt-2.7). Note
39 - 32 virtio-mmio transport devices
40 - running guests using the KVM accelerator on aarch64 hardware
41 - large amounts of RAM (at least 255GB, and more if using highmem)
42 - many CPUs (up to 512 if using a GICv3 and highmem)
43 - Secure-World-only devices if the CPU has TrustZone:
45   - A second PL011 UART
46   - A second PL061 GPIO controller, with GPIO lines for triggering
48   - A secure flash memory
49   - 16MB of secure RAM
52 explicitly (e.g. with a second -serial command line option) and
55 Supported guest CPU types:
57 - ``cortex-a7`` (32-bit)
58 - ``cortex-a15`` (32-bit; the default)
59 - ``cortex-a35`` (64-bit)
60 - ``cortex-a53`` (64-bit)
61 - ``cortex-a55`` (64-bit)
62 - ``cortex-a57`` (64-bit)
63 - ``cortex-a72`` (64-bit)
64 - ``cortex-a76`` (64-bit)
65 - ``cortex-a710`` (64-bit)
66 - ``a64fx`` (64-bit)
67 - ``host`` (with KVM only)
68 - ``neoverse-n1`` (64-bit)
69 - ``neoverse-v1`` (64-bit)
70 - ``neoverse-n2`` (64-bit)
71 - ``max`` (same as ``host`` for KVM; best possible emulation with TCG)
73 Note that the default is ``cortex-a15``, so for an AArch64 guest you must
74 specify a CPU type.
76 Also, please note that passing ``max`` CPU (i.e. ``-cpu max``) won't
77 enable all the CPU features for a given ``virt`` machine. Where a CPU
78 architectural feature requires support in both the CPU itself and in the
80 but instead requires a machine option to enable it.
82 For example, MTE support must be enabled with ``-machine virt,mte=on``,
83 as well as by selecting an MTE-capable CPU (e.g., ``max``) with the
84 ``-cpu`` option.
86 See the machine-specific options below, or check them for a given machine
87 by passing the ``help`` suboption, like: ``-machine virt-9.0,help``.
91 the Display devices section of "-device help". The recommended option
92 is ``virtio-gpu-pci``; this is the only one which will work correctly
93 with KVM. You may also need to ensure your guest kernel is configured
96 Machine-specific options
99 The following machine-specific options are supported:
102   Set ``on``/``off`` to enable/disable emulating a guest CPU which implements the
106   Set ``on``/``off`` to enable/disable emulating a guest CPU which implements the
110   Set ``on``/``off`` to enable/disable emulating a guest CPU which implements the
114   Set ``on``/``off`` to enable/disable placing devices and RAM in physical
116   later than ``virt-2.12`` when the CPU supports an address space
117   bigger than 32 bits (i.e. 64-bit CPUs, and 32-bit CPUs with the
118   Large Physical Address Extension (LPAE) feature). If you want to
119   boot a 32-bit kernel which does not have ``CONFIG_LPAE`` enabled on
120   a CPU type which implements LPAE, you will need to manually set
121   this to ``off``; otherwise some devices, such as the PCI controller,
124 compact-highmem
125   Set ``on``/``off`` to enable/disable the compact layout for high memory regions.
126   The default is ``on`` for machine types later than ``virt-7.2``.
128 highmem-redists
129   Set ``on``/``off`` to enable/disable the high memory region for GICv3 or
130   GICv4 redistributor. The default is ``on``. Setting this to ``off`` will
133 highmem-ecam
134   Set ``on``/``off`` to enable/disable the high memory region for PCI ECAM.
135   The default is ``on`` for machine types later than ``virt-3.0``.
137 highmem-mmio
138   Set ``on``/``off`` to enable/disable the high memory region for PCI MMIO.
141 gic-version
142   Specify the version of the Generic Interrupt Controller (GIC) to provide.
146     GICv2. Note that this limits the number of CPUs to 8.
148     GICv3. This allows up to 512 CPUs.
150     GICv4. Requires ``virtualization`` to be ``on``; allows up to 317 CPUs.
159   Set ``on``/``off`` to enable/disable ITS instantiation. The default is ``on``
160   for machine types later than ``virt-2.7``.
163   Set the IOMMU type to create for the guest. Valid values are:
171   Set ``on``/``off`` to enable/disable reporting host memory errors to a guest
174 dtb-randomness
175   Set ``on``/``off`` to pass random seeds via the guest DTB
176   rng-seed and kaslr-seed nodes (in both "/chosen" and
177   "/secure-chosen") to use for features like the random number
179   ``on``. You will want to disable it if your trusted boot chain
181   DTB to be non-deterministic. It would be the responsibility of
182   the firmware to come up with a seed and pass it on if it wants to.
184 dtb-kaslr-seed
185   A deprecated synonym for dtb-randomness.
191 right device drivers for virtio and the PCI controller; however some older
192 kernel versions, especially for 32-bit Arm, did not have everything
193 enabled by default. If you're not seeing PCI devices that you expect,
200 If you want to use the ``virtio-gpu-pci`` graphics device you will also
206 Hardware configuration information for bare-metal programming
210 which it passes to the guest. This provides information about the
212 in the system. Guest code can rely on and hard-code the following
215 - Flash memory starts at address 0x0000_0000
217 - RAM starts at 0x4000_0000
223 the way for the guest code to locate the dtb binary differs:
225 - For guests using the Linux kernel boot protocol (this means any
226   non-ELF file passed to the QEMU ``-kernel`` option) the address
227   of the DTB is passed in a register (``r2`` for 32-bit guests,
228   or ``x0`` for 64-bit guests)
230 - For guests booting as "bare-metal" (any other kind of boot),