Re: [RFC PATCH v3 4/5] platform/generic: Initialise MPT at boot

On Thu, Aug 6, 2026 at 12:09 AM Rahul Pathak
<[email protected]> wrote:
>
> Integrates MPT initialisation into the generic platform boot flow.
>
> mpt_early_init() probes for SMMPT during cold-boot early init and
> initialises the structures required to build MPT tables.
>
> mpt_final_init() creates the root supervisor domain which is mapping all
> physical memory with the firmware region explcitly denied to S-mode and
> adds support for an MPT domain for each additional registered SBI domain.
>
> The heap budget is extended to reserve space for MPT tables.
>
> With this patch MPT tables are built at boot.
>
> Signed-off-by: Rahul Pathak <[email protected]>

Initializing MPT from the generic platform is not the right way.

My suggestion is the following:
1) Call sbi_mpt_init() from sbi_hart_init() only when cold_boot == true
    right after sbi_hart_pmp_init() is called.
2) Instead of mpt_final_init(), the sbi_mpt_init() will register sbi_domain_data
    with distinct setup() and cleanup() callbacks which are called for each
    domain.

Regards,
Anup


> ---
>  platform/generic/platform.c | 101 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 101 insertions(+)
>
> diff --git a/platform/generic/platform.c b/platform/generic/platform.c
> index 1df0280d..b9a715b6 100644
> --- a/platform/generic/platform.c
> +++ b/platform/generic/platform.c
> @@ -17,6 +17,9 @@
>  #include <sbi/sbi_string.h>
>  #include <sbi/sbi_system.h>
>  #include <sbi/sbi_tlb.h>
> +#include <sbi/sbi_mpt.h>
> +#include <sbi/sbi_domain.h>
> +#include <sbi/sbi_console.h>
>  #include <sbi_utils/cache/fdt_cmo_helper.h>
>  #include <sbi_utils/fdt/fdt_domain.h>
>  #include <sbi_utils/fdt/fdt_driver.h>
> @@ -33,6 +36,86 @@
>  /* List of platform override modules generated at compile time */
>  extern const struct fdt_driver *const platform_override_modules[];
>
> +/*
> + * mpt_early_init(): Detects the SMMPT mode and initializes the
> + * structures (not MPT tables) requried to prepare MPT tables and
> + * domain programming.
> + */
> +int mpt_early_init(bool cold_boot)
> +{
> +       int rc;
> +
> +       if (!cold_boot)
> +               return 0;
> +
> +       rc = sbi_mpt_init();
> +       if (rc == SBI_ENODEV)
> +               return 0;
> +
> +       return rc;
> +}
> +
> +/*
> + * mpt_final_init(): Performs the final initialzation including
> + * creation of Root supervisor domain.
> + */
> +int mpt_final_init(bool cold_boot)
> +{
> +       int rc;
> +       u32 sdid;
> +       struct sbi_domain *dom, *root_dom;
> +       struct sbi_mpt_domain_config cfg;
> +
> +       if (!cold_boot)
> +               return 0;
> +
> +       /* SMMPT may be unavailable */
> +       if (!sbi_mpt_ctrl_get()->ready)
> +               return 0;
> +
> +       /*
> +        * Create MPT domain for Root domain.
> +        *
> +        * Root domain maps all physical memory so the
> +        * firmware region must be explicitly denied to S-mode.
> +        *
> +        * regions pointer is NULL and nregions is 0 since there
> +        * are no other regions other than respective SBI domain for mapping.
> +        */
> +       root_dom = sbi_domain_thishart_ptr();
> +       cfg.sbi_dom = root_dom;
> +       cfg.xwr = SBI_MPT_PERM_RWX;
> +       cfg.fw_protect = true;
> +       cfg.regions = NULL;
> +       cfg.nregions = 0;
> +
> +       rc = sbi_mpt_domain_create(&cfg, &sdid);
> +       if (rc) {
> +               sbi_printf("mpt: Root domain create failed rc=%d\n", rc);
> +               return rc;
> +       }
> +
> +       sbi_memset(&cfg, 0, sizeof(cfg));
> +
> +       /* Create MPT domain for all other registered SBI domains. */
> +       sbi_domain_for_each(dom) {
> +               if (dom == root_dom)
> +                       continue;
> +
> +               cfg.sbi_dom = dom;
> +               cfg.xwr = SBI_MPT_PERM_RWX;
> +               cfg.fw_protect = false;
> +               cfg.regions = NULL;
> +               cfg.nregions = 0;
> +
> +               rc = sbi_mpt_domain_create(&cfg, &sdid);
> +               if (rc)
> +                       sbi_printf("mpt: domain '%s' failed rc=%d\n", dom->name, rc);
> +       }
> +
> +       return 0;
> +}
> +
>  static u32 fw_platform_calculate_heap_size(u32 hart_count)
>  {
>         u32 heap_size;
> @@ -42,6 +125,15 @@ static u32 fw_platform_calculate_heap_size(u32 hart_count)
>         /* For TLB fifo */
>         heap_size += SBI_TLB_INFO_SIZE * (hart_count) * (hart_count);
>
> +       /*
> +        * MPT table budget
> +        * 1 MiB memory for MPT allocated currently.
> +        *
> +        * TODO: Need better way to get the memory budget based on active
> +        * SMMPT mode.
> +        */
> +       heap_size += 1024 * 1024;
> +
>         return BIT_ALIGN(heap_size, HEAP_BASE_ALIGN);
>  }
>
> @@ -229,6 +321,10 @@ int generic_early_init(bool cold_boot)
>                         return rc;
>
>                 fdt_driver_init_all(fdt, fdt_early_drivers);
> +
> +               rc = mpt_early_init(cold_boot);
> +               if (rc)
> +                       return rc;
>         }
>
>         return fdt_cmo_init(cold_boot);
> @@ -236,11 +332,16 @@ int generic_early_init(bool cold_boot)
>
>  int generic_final_init(bool cold_boot)
>  {
> +       int rc;
>         void *fdt = fdt_get_address_rw();
>
>         if (!cold_boot)
>                 return 0;
>
> +       rc = mpt_final_init(cold_boot);
> +       if (rc)
> +               return rc;
> +
>         fdt_cpu_fixup(fdt);
>         fdt_fixups(fdt);
>         fdt_domain_fixup(fdt);
> --
> 2.51.0
>
>
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