[PATCH 2/2] lib: utils: Use SBI_DOMAIN_MMIO to check MMIO device permissions

[Anup Patel]

On Sat, Nov 22, 2025 at 1:08 AM Samuel Holland
<samuel.holland at sifive.com> wrote:
>
> Drivers or platforms may create memory regions with the MMIO flag set
> that contain S-mode-accessible MMIO devices. This is strictly correct
> and should be allowed, along with the existing default case of
> S-mode-accessible MMIO devices appearing in non-MMIO memory regions.
> When passed SBI_DOMAIN_MMIO, sbi_domain_check_addr() will perform the
> correct set of permission checks.
>
> Signed-off-by: Samuel Holland <samuel.holland at sifive.com>

LGTM.

Reviewed-by: Anup Patel <anup at brainfault.org>

Applied this patch to the riscv/opensbi repo.

Thanks,
Anup

> ---
>
>  lib/utils/fdt/fdt_fixup.c             | 2 +-
>  lib/utils/mpxy/fdt_mpxy_rpmi_sysmsi.c | 3 ++-
>  2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/lib/utils/fdt/fdt_fixup.c b/lib/utils/fdt/fdt_fixup.c
> index f3fe8af9..b0ed20c8 100644
> --- a/lib/utils/fdt/fdt_fixup.c
> +++ b/lib/utils/fdt/fdt_fixup.c
> @@ -185,7 +185,7 @@ static void fdt_domain_based_fixup_one(void *fdt, int nodeoff)
>                 return;
>
>         if (!sbi_domain_check_addr(dom, reg_addr, dom->next_mode,
> -                                   SBI_DOMAIN_READ | SBI_DOMAIN_WRITE)) {
> +                                   SBI_DOMAIN_READ | SBI_DOMAIN_WRITE | SBI_DOMAIN_MMIO)) {
>                 rc = fdt_open_into(fdt, fdt, fdt_totalsize(fdt) + 32);
>                 if (rc < 0)
>                         return;
> diff --git a/lib/utils/mpxy/fdt_mpxy_rpmi_sysmsi.c b/lib/utils/mpxy/fdt_mpxy_rpmi_sysmsi.c
> index 94a5af8c..1dcc049e 100644
> --- a/lib/utils/mpxy/fdt_mpxy_rpmi_sysmsi.c
> +++ b/lib/utils/mpxy/fdt_mpxy_rpmi_sysmsi.c
> @@ -57,7 +57,8 @@ static int mpxy_rpmi_sysmis_xfer(void *context, struct mbox_chan *chan,
>                         sys_msi_address |= ((u64)le32_to_cpu(((u32 *)xfer->tx)[2])) << 32;
>                         if (!sbi_domain_check_addr_range(sbi_domain_thishart_ptr(),
>                                                          sys_msi_address, 0x4, PRV_S,
> -                                                        SBI_DOMAIN_READ | SBI_DOMAIN_WRITE)) {
> +                                                        SBI_DOMAIN_READ | SBI_DOMAIN_WRITE |
> +                                                        SBI_DOMAIN_MMIO)) {
>                                 ((u32 *)xfer->rx)[0] = cpu_to_le32(RPMI_ERR_INVALID_ADDR);
>                                 args->rx_data_len = sizeof(u32);
>                                 break;
> --
> 2.47.2
>
>
> --
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