linux-kernel - Re: [PATCH 27/29] x86/boot/e820: Simplify the e820__range

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Message-ID: <aAfG0fSVFVNciAqi@smile.fi.intel.com>
Date: Tue, 22 Apr 2025 19:41:53 +0300
From: Andy Shevchenko <andy@...nel.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...nel.org>,
	Borislav Petkov <bp@...en8.de>, Juergen Gross <jgross@...e.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Kees Cook <keescook@...omium.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mike Rapoport <rppt@...nel.org>,
	Paul Menzel <pmenzel@...gen.mpg.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: [PATCH 27/29] x86/boot/e820: Simplify the e820__range_remove()
 API

On Mon, Apr 21, 2025 at 08:52:07PM +0200, Ingo Molnar wrote:
> Right now e820__range_remove() has two parameters to control the
> E820 type of the range removed:
> 
> 	extern void e820__range_remove(u64 start, u64 size, enum e820_type old_type, bool check_type);
> 
> Since E820 types start at 1, zero has a natural meaning of 'no type.
> 
> Consolidate the (old_type,check_type) parameters into a single (filter_type)
> parameter:
> 
> 	extern void e820__range_remove(u64 start, u64 size, enum e820_type filter_type);
> 
> Note that both e820__mapped_raw_any() and e820__mapped_any()
> already have such semantics for their 'type' parameter, although
> it's currently not used with '0' by in-kernel code.
> 
> Also, the __e820__mapped_all() internal helper already has such
> semantics implemented as well, and the e820__get_entry_type() API
> uses the '0' type to such effect.
> 
> This simplifies not just e820__range_remove(), and synchronizes its
> use of type filters with other E820 API functions, but simplifies
> usage sites as well, such as parse_memmap_one(), beyond the reduction
> of the number of parameters:
> 
>   -               else if (from)
>   -                       e820__range_remove(start_at, mem_size, from, 1);
>                   else
>   -                       e820__range_remove(start_at, mem_size, 0, 0);
>   +                       e820__range_remove(start_at, mem_size, from);
> 
> The generated code gets smaller as well:
> 
> 	add/remove: 0/0 grow/shrink: 0/5 up/down: 0/-66 (-66)
> 
> 	Function                                     old     new   delta
> 	parse_memopt                                 112     107      -5
> 	efi_init                                    1048    1039      -9
> 	setup_arch                                  2719    2709     -10
> 	e820__range_remove                           283     273     -10
> 	parse_memmap_opt                             559     527     -32
> 
> 	Total: Before=22,675,600, After=22,675,534, chg -0.00%

>  extern void e820__range_add   (u64 start, u64 size, enum e820_type type);
>  extern u64  e820__range_update(u64 start, u64 size, enum e820_type old_type, enum e820_type new_type);
> -extern void e820__range_remove(u64 start, u64 size, enum e820_type old_type, bool check_type);
> +extern void e820__range_remove(u64 start, u64 size, enum e820_type filter_type);
>  extern u64  e820__range_update_table(struct e820_table *t, u64 start, u64 size, enum e820_type old_type, enum e820_type new_type);
>  
>  extern int  e820__update_table(struct e820_table *table);

Wondering if are going to get rid of 'extern' for the functions...

-- 
With Best Regards,
Andy Shevchenko