Re: [Qemu-devel] [Qemu-riscv] [PATCH 2/2] riscv: sifive_u: Update the plic hart config to support multicore

[Fabien Chouteau]

Hi Bin,

Thanks for this patch.

I know I am very late to the game but I have a comment here.

On 17/05/2019 17:51, Bin Meng wrote:
> +    /* create PLIC hart topology configuration string */
> +    plic_hart_config_len = (strlen(SIFIVE_U_PLIC_HART_CONFIG) + 1) * 
> smp_cpus;
> +    plic_hart_config = g_malloc0(plic_hart_config_len);
> +    for (i = 0; i < smp_cpus; i++) {
> +        if (i != 0) {
> +            strncat(plic_hart_config, ",", plic_hart_config_len);
> +        }
> +        strncat(plic_hart_config, SIFIVE_U_PLIC_HART_CONFIG,
> +                plic_hart_config_len);
> +        plic_hart_config_len -= (strlen(SIFIVE_U_PLIC_HART_CONFIG) + 1);
> +    }
> +

This will create up to 4 MS PLIC devices. However on the Unleashed FU540 the 
PLICs are M,MS,MS,MS,MS because of the monitor hart #0.

This means a different memory layout than the real hardware.

For instance address 0x0C00_2080 will be hart #0 S-Mode interrupt enables in 
QEMU, instead of #1 M-Mode interrupt enables for the real hardware.

To fix this I suggest to change this loop to:

    for (i = 0; i < smp_cpus; i++) {
        if (i != 0) {
            strncat(plic_hart_config, "," SIFIVE_U_PLIC_HART_CONFIG,
                    plic_hart_config_len);
        } else {
            strncat(plic_hart_config, "M", plic_hart_config_len);
        }
        plic_hart_config_len -= (strlen(SIFIVE_U_PLIC_HART_CONFIG) + 1);
    }

This will make hart #0 PLIC in M mode and the others in MS.

What do you think?

Best regards,