[RFC PATCH v2 41/48] efi_memory: add an event handler to update memory map

[Simon Glass]

Hi Sughosh,

On Thu, 4 Jul 2024 at 08:38, Sughosh Ganu <sughosh.ganu at linaro.org> wrote:
>
> There are events that would be used to notify other interested modules
> of any changes in available and occupied memory. This would happen
> when a module allocates or reserves memory, or frees up memory. These
> changes in memory map should be notified to other interested modules
> so that the allocated memory does not get overwritten. Add an event
> handler in the EFI memory module to update the EFI memory map
> accordingly when such changes happen. As a consequence, any subsequent
> memory request would honour the updated memory map and only available
> memory would be allocated from.
>
> Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> ---
> Changes since V1:
> * Handle the addition of memory to the LMB memory map.
> * Pass the overlap_only_ram parameter to the efi_add_memory_map_pg()
>   based on the type of operation.
>
>  lib/efi_loader/Kconfig      |  1 +
>  lib/efi_loader/efi_memory.c | 34 ++++++++++++++++++++++++++++++++++
>  2 files changed, 35 insertions(+)
>

This is getting complicated and I don't believe it is needed.

EFI should not be allocating memory 'in free space' until it starts
up. For the very few (if any) cases where it does, it can do an lmb
allocation.

As to the lmb allocations themselves, EFI can simply call look through
the lmb list and call efi_add_memory_map_pg() for each entry, when it
is ready to boot. There is no need to do it earlier.

> diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
> index bdf5732974..2d90bcef2f 100644
> --- a/lib/efi_loader/Kconfig
> +++ b/lib/efi_loader/Kconfig
> @@ -16,6 +16,7 @@ config EFI_LOADER
>         select CHARSET
>         # We need to send DM events, dynamically, in the EFI block driver
>         select DM_EVENT
> +       select EVENT
>         select EVENT_DYNAMIC
>         select LIB_UUID
>         select LMB
> diff --git a/lib/efi_loader/efi_memory.c b/lib/efi_loader/efi_memory.c
> index 5691b5da03..bd12504f72 100644
> --- a/lib/efi_loader/efi_memory.c
> +++ b/lib/efi_loader/efi_memory.c
> @@ -45,6 +45,10 @@ static LIST_HEAD(efi_mem);
>  void *efi_bounce_buffer;
>  #endif
>
> +#define MAP_OP_RESERVE         (u8)0x1
> +#define MAP_OP_FREE            (u8)0x2
> +#define MAP_OP_ADD             (u8)0x3
> +
>  /**
>   * struct efi_pool_allocation - memory block allocated from pool
>   *
> @@ -928,3 +932,33 @@ int efi_memory_init(void)
>
>         return 0;
>  }
> +
> +#if CONFIG_IS_ENABLED(MEM_MAP_UPDATE_NOTIFY)
> +static int lmb_mem_map_update_sync(void *ctx, struct event *event)
> +{
> +       u8 op;
> +       u64 addr;
> +       u64 pages;
> +       efi_status_t status;
> +       struct event_lmb_map_update *lmb_map = &event->data.lmb_map;
> +
> +       addr = (uintptr_t)map_sysmem(lmb_map->base, 0);
> +       pages = efi_size_in_pages(lmb_map->size + (addr & EFI_PAGE_MASK));
> +       op = lmb_map->op;
> +       addr &= ~EFI_PAGE_MASK;
> +
> +       if (op != MAP_OP_RESERVE && op != MAP_OP_FREE && op != MAP_OP_ADD) {
> +               log_debug("Invalid map update op received (%d)\n", op);
> +               return -1;
> +       }
> +
> +       status = efi_add_memory_map_pg(addr, pages,
> +                                      op == MAP_OP_RESERVE ?
> +                                      EFI_BOOT_SERVICES_DATA :
> +                                      EFI_CONVENTIONAL_MEMORY,
> +                                      op == MAP_OP_RESERVE ? true : false);
> +
> +       return status == EFI_SUCCESS ? 0 : -1;
> +}
> +EVENT_SPY_FULL(EVT_LMB_MAP_UPDATE, lmb_mem_map_update_sync);
> +#endif /* MEM_MAP_UPDATE_NOTIFY */
> --
> 2.34.1
>

Regards,
Simon