Re: [PATCH v2] mm: Fix memblock_free_late() when using deferred struct page

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Fri, 2026-02-20 at 11:09 +0200, Mike Rapoport wrote:
> 
> 
> Subject: [PATCH] x86/efi: defer freeing of boot services memory
> 
> ...
> 
> Make efi_free_boot_services() collect ranges that should be freed into
       ^^^^^^^^^^^^^^^^^^^^^^^

Reword "split efi_free_boot_services() in two. First
efi_unmap_boot_services() collects ..... then efi_free_boot_services()
later frees them after deferred init is complete."

IE. Your commit message still has the old names :)


That's my only comment.

Reviewed-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

> Link: https://lore.kernel.org/all/ec2aaef14783869b3be6e3c253b2dcbf67dbc12a.camel@kernel.crashing.org
> Fixes: 916f676f8dc0 ("x86, efi: Retain boot service code until after switching to virtual mode")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
>  arch/x86/include/asm/efi.h          |  2 +-
>  arch/x86/platform/efi/efi.c         |  2 +-
>  arch/x86/platform/efi/quirks.c      | 55 +++++++++++++++++++++++++++--
>  drivers/firmware/efi/mokvar-table.c |  2 +-
>  4 files changed, 55 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
> index f227a70ac91f..51b4cdbea061 100644
> --- a/arch/x86/include/asm/efi.h
> +++ b/arch/x86/include/asm/efi.h
> @@ -138,7 +138,7 @@ extern void __init efi_apply_memmap_quirks(void);
>  extern int __init efi_reuse_config(u64 tables, int nr_tables);
>  extern void efi_delete_dummy_variable(void);
>  extern void efi_crash_gracefully_on_page_fault(unsigned long phys_addr);
> -extern void efi_free_boot_services(void);
> +extern void efi_unmap_boot_services(void);
>  
>  void arch_efi_call_virt_setup(void);
>  void arch_efi_call_virt_teardown(void);
> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> index 463b784499a8..791c52c8393f 100644
> --- a/arch/x86/platform/efi/efi.c
> +++ b/arch/x86/platform/efi/efi.c
> @@ -837,7 +837,7 @@ static void __init __efi_enter_virtual_mode(void)
>  	}
>  
>  	efi_check_for_embedded_firmwares();
> -	efi_free_boot_services();
> +	efi_unmap_boot_services();
>  
>  	if (!efi_is_mixed())
>  		efi_native_runtime_setup();
> diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
> index 553f330198f2..35caa5746115 100644
> --- a/arch/x86/platform/efi/quirks.c
> +++ b/arch/x86/platform/efi/quirks.c
> @@ -341,7 +341,7 @@ void __init efi_reserve_boot_services(void)
>  
>  		/*
>  		 * Because the following memblock_reserve() is paired
> -		 * with memblock_free_late() for this region in
> +		 * 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
> @@ -404,17 +404,33 @@ static void __init efi_unmap_pages(efi_memory_desc_t *md)
>  		pr_err("Failed to unmap VA mapping for 0x%llx\n", va);
>  }
>  
> -void __init efi_free_boot_services(void)
> +struct efi_freeable_range {
> +	u64 start;
> +	u64 end;
> +};
> +
> +static struct efi_freeable_range *ranges_to_free;
> +
> +void __init efi_unmap_boot_services(void)
>  {
>  	struct efi_memory_map_data data = { 0 };
>  	efi_memory_desc_t *md;
>  	int num_entries = 0;
> +	int idx = 0;
> +	size_t sz;
>  	void *new, *new_md;
>  
>  	/* Keep all regions for /sys/kernel/debug/efi */
>  	if (efi_enabled(EFI_DBG))
>  		return;
>  
> +	sz = sizeof(*ranges_to_free) * efi.memmap.nr_map + 1;
> +	ranges_to_free = kzalloc(sz, GFP_KERNEL);
> +	if (!ranges_to_free) {
> +		pr_err("Failed to allocate storage for freeable EFI regions\n");
> +		return;
> +	}
> +
>  	for_each_efi_memory_desc(md) {
>  		unsigned long long start = md->phys_addr;
>  		unsigned long long size = md->num_pages << EFI_PAGE_SHIFT;
> @@ -471,7 +487,15 @@ void __init efi_free_boot_services(void)