Re: [RFCv2 PATCH 2/6] efi/unaccepted: Set unaccepted bits for all hotplug memory

[Kiryl Shutsemau <kas@kernel.org>]

On Tue, Jun 23, 2026 at 06:17:33AM -0400, Zhenzhong Duan wrote:
> In coco guests, hotpluggable memory ranges are initially unaccepted.
> While a previous change expanded the unaccepted memory bitmap boundaries
> to include these hotplug spaces, the actual bits inside the bitmap are
> not yet marked as unaccepted.
> 
> Walks SRAT a second time after the bitmap is allocated and sets the bits
> corresponding to hotpluggable ranges.
> 
> This ensures the bitmap state accurately reflects all static and hotplug
> memory ranges before booting kernel.
> 
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> ---
>  .../firmware/efi/libstub/unaccepted_memory.c   | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/firmware/efi/libstub/unaccepted_memory.c b/drivers/firmware/efi/libstub/unaccepted_memory.c
> index bfbb78bd7b8a..01bed8e751ca 100644
> --- a/drivers/firmware/efi/libstub/unaccepted_memory.c
> +++ b/drivers/firmware/efi/libstub/unaccepted_memory.c
> @@ -92,6 +92,23 @@ static void update_mem_boundaries(struct acpi_srat_mem_affinity *mem, struct sra
>  		*(ctx->mem_end) = range_end;
>  }
>  
> +static void mark_hotplug_memory_unaccepted(struct acpi_srat_mem_affinity *mem,
> +					   struct srat_parse_ctx *ctx)
> +{
> +	u64 unit_size = unaccepted_table->unit_size;
> +	u64 start, end;
> +
> +	start = round_up(mem->base_address, unit_size);
> +	end = round_down(mem->base_address + mem->length, unit_size);

We can get here with start > end if srat range is less then unit_size.

> +
> +	/* Translate to offsets from the beginning of the bitmap */
> +	start -= unaccepted_table->phys_base;
> +	end -= unaccepted_table->phys_base;
> +
> +	bitmap_set(unaccepted_table->bitmap,
> +		   start / unit_size, (end - start) / unit_size);
> +}
> +
>  efi_status_t allocate_unaccepted_bitmap(__u32 nr_desc,
>  					struct efi_boot_memmap *map)
>  {
> @@ -169,6 +186,7 @@ efi_status_t allocate_unaccepted_bitmap(__u32 nr_desc,
>  	unaccepted_table->phys_base = unaccepted_start;
>  	unaccepted_table->size = bitmap_size;
>  	memset(unaccepted_table->bitmap, 0, bitmap_size);
> +	parse_acpi_srat_regions(mark_hotplug_memory_unaccepted, &ctx);
>  
>  	status = efi_bs_call(install_configuration_table,
>  			     &unaccepted_table_guid, unaccepted_table);
> -- 
> 2.52.0
> 

-- 
  Kiryl Shutsemau / Kirill A. Shutemov