Re: [PATCH V19 4/5] hw/mips: Add Loongson-3 machine support

[Philippe Mathieu-Daudé]

Hi Huacai,

On 12/21/20 12:05 PM, Huacai Chen wrote:
> Add Loongson-3 based machine support, it use liointc as the interrupt
> controler and use GPEX as the pci controller. Currently it can work with
> both TCG and KVM.
> 
> As the machine model is not based on any exiting physical hardware, the
> name of the machine is "loongson3-virt". It may be superseded in future
> by a real machine model. If this happens, then a regular deprecation
> procedure shall occur for "loongson3-virt" machine.
> 
> We now already have a full functional Linux kernel (based on Linux-5.4.x
> LTS) here:
> 
> https://github.com/chenhuacai/linux

Can you point to a tag/commit? (Thinking about looking at this
commit in few years from now).

> Of course the upstream kernel is also usable (the kvm host side and
> guest side have both been upstream in Linux-5.9):
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> 
> How to use QEMU/Loongson-3?
> 1, Download kernel source from the above URL;
> 2, Build a kernel with arch/mips/configs/loongson3_defconfig;
> 3, Boot a Loongson-3A4000 host with this kernel (for KVM mode);
> 4, Build QEMU-master with this patchset;
> 5, modprobe kvm (only necessary for KVM mode);
> 6, Use QEMU with TCG:
>        qemu-system-mips64el -M loongson3-virt,accel=tcg -cpu Loongson-3A1000 
> -kernel <path_to_kernel> -append ...
>    Use QEMU with KVM:
>        qemu-system-mips64el -M loongson3-virt,accel=kvm -cpu Loongson-3A4000 
> -kernel <path_to_kernel> -append ...
> 
>    The "-cpu" parameter is optional here and QEMU will use the correct type 
> for TCG/KVM automatically.
> 
> Signed-off-by: Huacai Chen <chenhuacai@kernel.org>
> Co-developed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> ---
>  MAINTAINERS                                  |   1 +
>  default-configs/devices/mips64el-softmmu.mak |   1 +
>  hw/mips/Kconfig                              |  11 +
>  hw/mips/loongson3_virt.c                     | 621 +++++++++++++++++++
>  hw/mips/meson.build                          |   2 +-
>  5 files changed, 635 insertions(+), 1 deletion(-)
>  create mode 100644 hw/mips/loongson3_virt.c
...

> +    /*
> +     * The whole MMIO range among configure registers doesn't generate
> +     * exception when accessing invalid memory. Create some unimplememted
> +     * devices to emulate this feature.
> +     */
> +    create_unimplemented_device("mmio fallback 0", 0x10000000, 256 * MiB);
> +    create_unimplemented_device("mmio fallback 1", 0x30000000, 256 * MiB);
> +
> +    liointc = qdev_new("loongson.liointc");
> +    sysbus_realize_and_unref(SYS_BUS_DEVICE(liointc), &error_fatal);
> +
> +    sysbus_mmio_map(SYS_BUS_DEVICE(liointc), 0, 
> virt_memmap[VIRT_LIOINTC].base);
> +
> +    serial_mm_init(address_space_mem, virt_memmap[VIRT_UART].base, 0,
> +                   qdev_get_gpio_in(liointc, UART_IRQ), 115200, serial_hd(0),
> +                   DEVICE_NATIVE_ENDIAN);
> +
> +    sysbus_create_simple("goldfish_rtc", virt_memmap[VIRT_RTC].base,
> +                         qdev_get_gpio_in(liointc, RTC_IRQ));
> +
> +    cpuclk = clock_new(OBJECT(machine), "cpu-refclk");
> +    clock_set_hz(cpuclk, DEF_LOONGSON3_FREQ);

Shouldn't this be:

       clock_set_hz(cpuclk, get_cpu_freq_hz());

?

> +
> +    for (i = 0; i < machine->smp.cpus; i++) {
> +        int ip;
> +
> +        /* init CPUs */
> +        cpu = mips_cpu_create_with_clock(machine->cpu_type, cpuclk);
> +
> +        /* Init internal devices */
> +        cpu_mips_irq_init_cpu(cpu);
> +        cpu_mips_clock_init(cpu);
> +        qemu_register_reset(main_cpu_reset, cpu);
> +
> +        if (i >= 4) {
> +            continue; /* Only node-0 can be connected to LIOINTC */
> +        }
> +
> +        for (ip = 0; ip < 4 ; ip++) {
> +            int pin = i * 4 + ip;
> +            sysbus_connect_irq(SYS_BUS_DEVICE(liointc),
> +                               pin, cpu->env.irq[ip + 2]);
> +        }
> +    }
> +    env = &MIPS_CPU(first_cpu)->env;
...