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| -rw-r--r-- | MAINTAINERS | 1 | ||||
| -rw-r--r-- | docs/system/arm/virt.rst | 161 | ||||
| -rw-r--r-- | docs/system/target-arm.rst | 1 |
3 files changed, 163 insertions, 0 deletions
diff --git a/MAINTAINERS b/MAINTAINERS index 935ccb3ab3..5e8616821a 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -880,6 +880,7 @@ L: qemu-arm@nongnu.org S: Maintained F: hw/arm/virt* F: include/hw/arm/virt.h +F: docs/system/arm/virt.rst Xilinx Zynq M: Edgar E. Iglesias <edgar.iglesias@gmail.com> diff --git a/docs/system/arm/virt.rst b/docs/system/arm/virt.rst new file mode 100644 index 0000000000..6621ab7205 --- /dev/null +++ b/docs/system/arm/virt.rst @@ -0,0 +1,161 @@ +'virt' generic virtual platform (``virt``) +========================================== + +The `virt` board is a platform which does not correspond to any +real hardware; it is designed for use in virtual machines. +It is the recommended board type if you simply want to run +a guest such as Linux and do not care about reproducing the +idiosyncrasies and limitations of a particular bit of real-world +hardware. + +This is a "versioned" board model, so as well as the ``virt`` machine +type itself (which may have improvements, bugfixes and other minor +changes between QEMU versions) a version is provided that guarantees +to have the same behaviour as that of previous QEMU releases, so +that VM migration will work between QEMU versions. For instance the +``virt-5.0`` machine type will behave like the ``virt`` machine from +the QEMU 5.0 release, and migration should work between ``virt-5.0`` +of the 5.0 release and ``virt-5.0`` of the 5.1 release. Migration +is not guaranteed to work between different QEMU releases for +the non-versioned ``virt`` machine type. + +Supported devices +""""""""""""""""" + +The virt board supports: + +- PCI/PCIe devices +- Flash memory +- One PL011 UART +- An RTC +- The fw_cfg device that allows a guest to obtain data from QEMU +- A PL061 GPIO controller +- An optional SMMUv3 IOMMU +- hotpluggable DIMMs +- hotpluggable NVDIMMs +- An MSI controller (GICv2M or ITS). GICv2M is selected by default along + with GICv2. ITS is selected by default with GICv3 (>= virt-2.7). Note + that ITS is not modeled in TCG mode. +- 32 virtio-mmio transport devices +- running guests using the KVM accelerator on aarch64 hardware +- large amounts of RAM (at least 255GB, and more if using highmem) +- many CPUs (up to 512 if using a GICv3 and highmem) +- Secure-World-only devices if the CPU has TrustZone: + + - A second PL011 UART + - A secure flash memory + - 16MB of secure RAM + +Supported guest CPU types: + +- ``cortex-a7`` (32-bit) +- ``cortex-a15`` (32-bit; the default) +- ``cortex-a53`` (64-bit) +- ``cortex-a57`` (64-bit) +- ``cortex-a72`` (64-bit) +- ``host`` (with KVM only) +- ``max`` (same as ``host`` for KVM; best possible emulation with TCG) + +Note that the default is ``cortex-a15``, so for an AArch64 guest you must +specify a CPU type. + +Graphics output is available, but unlike the x86 PC machine types +there is no default display device enabled: you should select one from +the Display devices section of "-device help". The recommended option +is ``virtio-gpu-pci``; this is the only one which will work correctly +with KVM. You may also need to ensure your guest kernel is configured +with support for this; see below. + +Machine-specific options +"""""""""""""""""""""""" + +The following machine-specific options are supported: + +secure + Set ``on``/``off`` to enable/disable emulating a guest CPU which implements the + Arm Security Extensions (TrustZone). The default is ``off``. + +virtualization + Set ``on``/``off`` to enable/disable emulating a guest CPU which implements the + Arm Virtualization Extensions. The default is ``off``. + +highmem + Set ``on``/``off`` to enable/disable placing devices and RAM in physical + address space above 32 bits. The default is ``on`` for machine types + later than ``virt-2.12``. + +gic-version + Specify the version of the Generic Interrupt Controller (GIC) to provide. + Valid values are: + + ``2`` + GICv2 + ``3`` + GICv3 + ``host`` + Use the same GIC version the host provides, when using KVM + ``max`` + Use the best GIC version possible (same as host when using KVM; + currently same as ``3``` for TCG, but this may change in future) + +its + Set ``on``/``off`` to enable/disable ITS instantiation. The default is ``on`` + for machine types later than ``virt-2.7``. + +iommu + Set the IOMMU type to create for the guest. Valid values are: + + ``none`` + Don't create an IOMMU (the default) + ``smmuv3`` + Create an SMMUv3 + +ras + Set ``on``/``off`` to enable/disable reporting host memory errors to a guest + using ACPI and guest external abort exceptions. The default is off. + +Linux guest kernel configuration +"""""""""""""""""""""""""""""""" + +The 'defconfig' for Linux arm and arm64 kernels should include the +right device drivers for virtio and the PCI controller; however some older +kernel versions, especially for 32-bit Arm, did not have everything +enabled by default. If you're not seeing PCI devices that you expect, +then check that your guest config has:: + + CONFIG_PCI=y + CONFIG_VIRTIO_PCI=y + CONFIG_PCI_HOST_GENERIC=y + +If you want to use the ``virtio-gpu-pci`` graphics device you will also +need:: + + CONFIG_DRM=y + CONFIG_DRM_VIRTIO_GPU=y + +Hardware configuration information for bare-metal programming +""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" + +The ``virt`` board automatically generates a device tree blob ("dtb") +which it passes to the guest. This provides information about the +addresses, interrupt lines and other configuration of the various devices +in the system. Guest code can rely on and hard-code the following +addresses: + +- Flash memory starts at address 0x0000_0000 + +- RAM starts at 0x4000_0000 + +All other information about device locations may change between +QEMU versions, so guest code must look in the DTB. + +QEMU supports two types of guest image boot for ``virt``, and +the way for the guest code to locate the dtb binary differs: + +- For guests using the Linux kernel boot protocol (this means any + non-ELF file passed to the QEMU ``-kernel`` option) the address + of the DTB is passed in a register (``r2`` for 32-bit guests, + or ``x0`` for 64-bit guests) + +- For guests booting as "bare-metal" (any other kind of boot), + the DTB is at the start of RAM (0x4000_0000) diff --git a/docs/system/target-arm.rst b/docs/system/target-arm.rst index 163ab91559..4c5b0e4aab 100644 --- a/docs/system/target-arm.rst +++ b/docs/system/target-arm.rst @@ -92,6 +92,7 @@ undocumented; you can get a complete list by running arm/collie arm/sx1 arm/stellaris + arm/virt Arm CPU features ================ |