[RFC PATCH 3/3] sifive_dev_platform: Set default MMIO region when SmePMP is enabled

[Anup Patel]

On Tue, Feb 24, 2026 at 8:47 AM Yu-Chien Peter Lin <peter.lin at sifive.com> wrote:
>
> Set a default MMIO region with a single SmePMP entry, which allows us
> to save entries for M-mode only devices. The default entry has M-/S-mode
> shared permission, so system-level resource protection, such as RISC-V
> World extension and WorldGuard checker, will be introduced to protect
> M-mode only region access from lower privilege modes.
>
> Reviewed-by: Greentime Hu <greentime.hu at sifive.com>
> Reviewed-by: Zong Li <zong.li at sifive.com>
> Signed-off-by: Yu-Chien Peter Lin <peter.lin at sifive.com>
> ---
>  platform/generic/sifive/sifive_dev_platform.c | 48 +++++++++++++++++++
>  1 file changed, 48 insertions(+)
>
> diff --git a/platform/generic/sifive/sifive_dev_platform.c b/platform/generic/sifive/sifive_dev_platform.c
> index facc044f1..9799e5b88 100644
> --- a/platform/generic/sifive/sifive_dev_platform.c
> +++ b/platform/generic/sifive/sifive_dev_platform.c
> @@ -5,10 +5,58 @@
>   */
>
>  #include <platform_override.h>
> +#include <sbi/sbi_hart.h>
> +#include <sbi/sbi_scratch.h>
> +
> +/*
> + * Instead of allocating individual PMP entries for each M-mode
> + * MMIO driver, configure SMEPMP regions to grant R/W permission
> + * to peripheral and system ports for all privilege modes.
> + * Finer-grained access control is enforced by wgChecker rules.
> + */
> +static int sifive_smepmp_setup(void)
> +{
> +       struct sbi_scratch *scratch = sbi_scratch_thishart_ptr();
> +       int rc;
> +
> +       if (!sbi_hart_has_extension(scratch, SBI_HART_EXT_SMEPMP))
> +               return 0;
> +
> +       /* Peripheral port region: 0 to 2GiB */
> +       rc = sbi_domain_root_add_memrange(0x0, 0x80000000, 0x80000000,
> +                                         SBI_DOMAIN_MEMREGION_MMIO |
> +                                         SBI_DOMAIN_MEMREGION_SHARED_SURW_MRW);
> +       if (rc)
> +               return rc;
> +
> +       /* System port region: 512GiB to 1TiB */
> +       rc = sbi_domain_root_add_memrange(0x8000000000, 0x8000000000, 0x8000000000,
> +                                         SBI_DOMAIN_MEMREGION_MMIO |
> +                                         SBI_DOMAIN_MEMREGION_SHARED_SURW_MRW);
> +       if (rc)
> +               return rc;

This breaks compilation of generic platform on RV32 because
addresses are beyond 32-bit space. I have put #if at the time
of merging.

> +
> +       return 0;
> +}
> +
> +static int sifive_early_init(bool cold_boot)
> +{
> +       int rc;
> +
> +       if (cold_boot) {
> +               rc = sifive_smepmp_setup();
> +               if (rc)
> +                       return rc;
> +       }
> +
> +       return generic_early_init(cold_boot);
> +}
>
>  static int sifive_platform_init(const void *fdt, int nodeoff,
>                                 const struct fdt_match *match)
>  {
> +       generic_platform_ops.early_init = sifive_early_init;
> +
>         return 0;
>  }
>
> --
> 2.43.7
>
>
> --
> opensbi mailing list
> opensbi at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/opensbi

Applied this patch to the riscv/opensbi repo.

Thanks,
Anup