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[PULL v2 04/12] docs/system: riscv: Add documentation for virt machine
From: |
Alistair Francis |
Subject: |
[PULL v2 04/12] docs/system: riscv: Add documentation for virt machine |
Date: |
Thu, 15 Jul 2021 00:16:32 -0700 |
From: Bin Meng <bmeng.cn@gmail.com>
This adds detailed documentation for RISC-V `virt` machine,
including the following information:
- Supported devices
- Hardware configuration information
- Boot options
- Running Linux kernel
- Running U-Boot
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20210627142816.19789-2-bmeng.cn@gmail.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
---
docs/system/riscv/virt.rst | 138 +++++++++++++++++++++++++++++++++++
docs/system/target-riscv.rst | 1 +
2 files changed, 139 insertions(+)
create mode 100644 docs/system/riscv/virt.rst
diff --git a/docs/system/riscv/virt.rst b/docs/system/riscv/virt.rst
new file mode 100644
index 0000000000..3709f05797
--- /dev/null
+++ b/docs/system/riscv/virt.rst
@@ -0,0 +1,138 @@
+'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.
+
+Supported devices
+-----------------
+
+The ``virt`` machine supports the following devices:
+
+* Up to 8 generic RV32GC/RV64GC cores, with optional extensions
+* Core Local Interruptor (CLINT)
+* Platform-Level Interrupt Controller (PLIC)
+* CFI parallel NOR flash memory
+* 1 NS16550 compatible UART
+* 1 Google Goldfish RTC
+* 1 SiFive Test device
+* 8 virtio-mmio transport devices
+* 1 generic PCIe host bridge
+* The fw_cfg device that allows a guest to obtain data from QEMU
+
+Note that the default CPU is a generic RV32GC/RV64GC. Optional extensions
+can be enabled via command line parameters, e.g.: ``-cpu rv64,x-h=true``
+enables the hypervisor extension for RV64.
+
+Hardware configuration information
+----------------------------------
+
+The ``virt`` machine automatically generates a device tree blob ("dtb")
+which it passes to the guest, if there is no ``-dtb`` option. This provides
+information about the addresses, interrupt lines and other configuration of
+the various devices in the system. Guest software should discover the devices
+that are present in the generated DTB.
+
+If users want to provide their own DTB, they can use the ``-dtb`` option.
+These DTBs should have the following requirements:
+
+* The number of subnodes of the /cpus node should match QEMU's ``-smp`` option
+* The /memory reg size should match QEMU’s selected ram_size via ``-m``
+* Should contain a node for the CLINT device with a compatible string
+ "riscv,clint0" if using with OpenSBI BIOS images
+
+Boot options
+------------
+
+The ``virt`` machine can start using the standard -kernel functionality
+for loading a Linux kernel, a VxWorks kernel, an S-mode U-Boot bootloader
+with the default OpenSBI firmware image as the -bios. It also supports
+the recommended RISC-V bootflow: U-Boot SPL (M-mode) loads OpenSBI fw_dynamic
+firmware and U-Boot proper (S-mode), using the standard -bios functionality.
+
+Running Linux kernel
+--------------------
+
+Linux mainline v5.12 release is tested at the time of writing. To build a
+Linux mainline kernel that can be booted by the ``virt`` machine in
+64-bit mode, simply configure the kernel using the defconfig configuration:
+
+.. code-block:: bash
+
+ $ export ARCH=riscv
+ $ export CROSS_COMPILE=riscv64-linux-
+ $ make defconfig
+ $ make
+
+To boot the newly built Linux kernel in QEMU with the ``virt`` machine:
+
+.. code-block:: bash
+
+ $ qemu-system-riscv64 -M virt -smp 4 -m 2G \
+ -display none -serial stdio \
+ -kernel arch/riscv/boot/Image \
+ -initrd /path/to/rootfs.cpio \
+ -append "root=/dev/ram"
+
+To build a Linux mainline kernel that can be booted by the ``virt`` machine
+in 32-bit mode, use the rv32_defconfig configuration. A patch is required to
+fix the 32-bit boot issue for Linux kernel v5.12.
+
+.. code-block:: bash
+
+ $ export ARCH=riscv
+ $ export CROSS_COMPILE=riscv64-linux-
+ $ curl
https://patchwork.kernel.org/project/linux-riscv/patch/20210627135117.28641-1-bmeng.cn@gmail.com/mbox/
> riscv.patch
+ $ git am riscv.patch
+ $ make rv32_defconfig
+ $ make
+
+Replace ``qemu-system-riscv64`` with ``qemu-system-riscv32`` in the command
+line above to boot the 32-bit Linux kernel. A rootfs image containing 32-bit
+applications shall be used in order for kernel to boot to user space.
+
+Running U-Boot
+--------------
+
+U-Boot mainline v2021.04 release is tested at the time of writing. To build an
+S-mode U-Boot bootloader that can be booted by the ``virt`` machine, use
+the qemu-riscv64_smode_defconfig with similar commands as described above for
Linux:
+
+.. code-block:: bash
+
+ $ export CROSS_COMPILE=riscv64-linux-
+ $ make qemu-riscv64_smode_defconfig
+
+Boot the 64-bit U-Boot S-mode image directly:
+
+.. code-block:: bash
+
+ $ qemu-system-riscv64 -M virt -smp 4 -m 2G \
+ -display none -serial stdio \
+ -kernel /path/to/u-boot.bin
+
+To test booting U-Boot SPL which in M-mode, which in turn loads a FIT image
+that bundles OpenSBI fw_dynamic firmware and U-Boot proper (S-mode) together,
+build the U-Boot images using riscv64_spl_defconfig:
+
+.. code-block:: bash
+
+ $ export CROSS_COMPILE=riscv64-linux-
+ $ export OPENSBI=/path/to/opensbi-riscv64-generic-fw_dynamic.bin
+ $ make qemu-riscv64_spl_defconfig
+
+The minimal QEMU commands to run U-Boot SPL are:
+
+.. code-block:: bash
+
+ $ qemu-system-riscv64 -M virt -smp 4 -m 2G \
+ -display none -serial stdio \
+ -bios /path/to/u-boot-spl \
+ -device loader,file=/path/to/u-boot.itb,addr=0x80200000
+
+To test 32-bit U-Boot images, switch to use qemu-riscv32_smode_defconfig and
+riscv32_spl_defconfig builds, and replace ``qemu-system-riscv64`` with
+``qemu-system-riscv32`` in the command lines above to boot the 32-bit U-Boot.
diff --git a/docs/system/target-riscv.rst b/docs/system/target-riscv.rst
index a5cc06b726..89a866e4f4 100644
--- a/docs/system/target-riscv.rst
+++ b/docs/system/target-riscv.rst
@@ -69,6 +69,7 @@ undocumented; you can get a complete list by running
riscv/microchip-icicle-kit
riscv/shakti-c
riscv/sifive_u
+ riscv/virt
RISC-V CPU firmware
-------------------
--
2.31.1
- [PULL v2 00/12] riscv-to-apply queue, Alistair Francis, 2021/07/15
- [PULL v2 01/12] target/riscv: pmp: Fix some typos, Alistair Francis, 2021/07/15
- [PULL v2 02/12] target/riscv: csr: Remove redundant check in fp csr read/write routines, Alistair Francis, 2021/07/15
- [PULL v2 03/12] docs/system: riscv: Fix CLINT name in the sifive_u doc, Alistair Francis, 2021/07/15
- [PULL v2 04/12] docs/system: riscv: Add documentation for virt machine,
Alistair Francis <=
- [PULL v2 05/12] target/riscv: hardwire bits in hideleg and hedeleg, Alistair Francis, 2021/07/15
- [PULL v2 06/12] docs/system: riscv: Update Microchip Icicle Kit for direct kernel boot, Alistair Francis, 2021/07/15
- [PULL v2 07/12] hw/riscv: sifive_u: Correct the CLINT timebase frequency, Alistair Francis, 2021/07/15
- [PULL v2 08/12] hw/riscv: sifive_u: Make sure firmware info is 8-byte aligned, Alistair Francis, 2021/07/15
- [PULL v2 09/12] char: ibex_uart: Update the register layout, Alistair Francis, 2021/07/15
- [PULL v2 11/12] hw/riscv: opentitan: Add the flash alias, Alistair Francis, 2021/07/15
- [PULL v2 10/12] hw/riscv: opentitan: Add the unimplement rv_core_ibex_peri, Alistair Francis, 2021/07/15
- [PULL v2 12/12] hw/riscv/boot: Check the error of fdt_pack(), Alistair Francis, 2021/07/15
- Re: [PULL v2 00/12] riscv-to-apply queue, Peter Maydell, 2021/07/16