Re: [PATCH v3 01/17] x86/efi: Omit redundant kernel image overlap check

[Gregory Price]

On Thu, Apr 23, 2026 at 05:20:26PM +0200, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@xxxxxxxxxx>
> 
> The physical region covering the kernel's executable image is
> memblock_reserve()'d in early_mem_reserve(), and so it is guaranteed not
> to intersect with the regions passed to can_free_region(). So remove the
> pointless overlap check.
> 
> Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>

Reviewed-by: Gregory Price <gourry@xxxxxxxxxx>

> ---
>  arch/x86/platform/efi/quirks.c | 15 ++++-----------
>  1 file changed, 4 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
> index df24ffc6105d..4d8de7c6ce59 100644
> --- a/arch/x86/platform/efi/quirks.c
> +++ b/arch/x86/platform/efi/quirks.c
> @@ -305,16 +305,11 @@ void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size)
>   * can free regions in efi_free_boot_services().
>   *
>   * Use this function to ensure we do not free regions owned by somebody
> - * else. We must only reserve (and then free) regions:
> - *
> - * - Not within any part of the kernel
> - * - Not the BIOS reserved area (E820_TYPE_RESERVED, E820_TYPE_NVS, etc)
> + * else. We must only reserve (and then free) regions that do not intersect
> + * with the BIOS reserved area (E820_TYPE_RESERVED, E820_TYPE_NVS, etc)
>   */
>  static __init bool can_free_region(u64 start, u64 size)
>  {
> -	if (start + size > __pa_symbol(_text) && start <= __pa_symbol(_end))
> -		return false;
> -
>  	if (!e820__mapped_all(start, start+size, E820_TYPE_RAM))
>  		return false;
>  
> @@ -343,10 +338,8 @@ void __init efi_reserve_boot_services(void)
>  		 * Because the following memblock_reserve() is paired
>  		 * with free_reserved_area() for this region in
>  		 * efi_free_boot_services(), we must be extremely
> -		 * careful not to reserve, and subsequently free,
> -		 * critical regions of memory (like the kernel image) or
> -		 * those regions that somebody else has already
> -		 * reserved.
> +		 * careful not to reserve, and subsequently free, critical
> +		 * regions of memory that somebody else has already reserved.
>  		 *
>  		 * A good example of a critical region that must not be
>  		 * freed is page zero (first 4Kb of memory), which may
> -- 
> 2.54.0.rc2.544.gc7ae2d5bb8-goog
>