On Mon, Jun 28, 2021 at 12:29 AM Bin Meng <bmeng...@gmail.com> wrote: > > 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...@gmail.com>
Thanks! Applied to riscv-to-apply.next Alistair > --- > > 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...@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 > ------------------- > -- > 2.25.1 > >